Traf fi c Volume
Passenger Transportation
Figure17.1reports passenger traffic volume in the European Union from 1970 to
2001, broken down according to the primary passenger transportation vehicles, such as cars, buses, urban railways with subways, trains and airplanes.
Cars are the dominant mode of transportation, accounting for over 78% of total traffic in 2001, with tire-based vehicles, including cars and buses, making up approximately 87% This distribution has remained relatively consistent over the years.
Over the first twenty years analyzed, the total volume experienced an annual growth of around 4%, but this growth stagnated to nearly zero in the subsequent years Notably, air transportation stands out as an exception, continuing to develop consistently despite the overall trend.
A similar table is reported for the following years in Fig.17.2 The total value is at present almost steady, around 6,500 Gpass×km as well as the modes breakdown.
Transportation of Goods
Figure17.3shows the volume of transportation of goods in the European Union from
1970 to 2001, broken down according to the main travel modes; in this case, road,rail, inland and sea navigation, and pipeline transportation are considered.
Year Cars Buses Urb railroads Railroads Aircraft Total
Passenger traffic volume in the European Union (EU 15) from 1970 to 2001 reached significant levels, measured in billions of passenger kilometers This data highlights the usage of various vehicle types, including airplanes, railroads, urban rail systems such as subways, buses, and cars, illustrating the evolving transportation landscape in the region Source: ANFIA.
Road transportation has become the dominant mode of transport, increasing from 35% in 1970 to 45% by the end of the last year analyzed In contrast, the share of railroads has significantly declined from 20% to just 8% in 2001 Additionally, sea navigation plays a significant role due to the longer distances covered.
Figure17.4reports a similar table for the following years Here the influence of the economy cycle can be noticed.
Year Cars Buses Motorbykes Urban tr Railroads Airplanes Sea Total
Between 1995 and 2015, passenger traffic volume in the European Union (EU 28) varied significantly, measured in billions of passenger kilometers This data, sourced from Eurostat, highlights the distribution of traffic across various vehicle types, including airplanes, railroads, urban rail systems like subways, buses, cars, and ships.
In recent years, developed countries have experienced a steady increase in transportation demand, driven by various factors such as economic and fiscal integration and market globalization This growth trend is expected to continue in the medium term.
The most stimulating factor was the European economic integration process,implying free transfer of goods in the Union.
Year Road Railroad Inland navigation Oil pipelines Sea navigation Total
Between 1970 and 2001, the transportation of goods within the European Union (EU 15) experienced significant changes, measured in billions of ton-kilometers This data encompasses various modes of transport, including road, rail, inland waterways, oil pipelines, and maritime shipping, as reported by ANFIA.
Energy Consumption
Energy consumption is typically quantified in tons of equivalent petroleum (tep), which equates to approximately 41.87 GJ or 11.63 MWh This measurement reflects the heat generated from burning a ton of average-quality oil Additionally, this unit is utilized to assess energy from various sources, based on the energy cost associated with their production.
Year Road See navigation Inland navigation Railroad Air
Between 1995 and 2015, the transportation of goods within the European Union (EU 28) saw significant changes, measured in billions of ton-kilometers This data, sourced from Eurostat, categorizes transportation modes into road, railroad, inland navigation, oil pipelines, and sea navigation, highlighting the diverse methods used for goods movement across the region.
Railroad transportation relies on a mix of electric energy and oil refinery products, with electric energy generated from thermal power stations that utilize oil products or natural gas, as well as from hydroelectric power stations Additionally, geothermal and nuclear energy sources also contribute to the overall energy supply for this mode of transport.
Every contribution is converted to an oil value, considering production losses and thermal equivalence.
Figure17.5 displays a time series of energy consumption in Europe for most important final applications.
The energy consumption of the transportation system is about 34% of the total in 2014; this share can be broken into:
The total figure for navigation in the European Union encompasses river, lake, channel, and sea navigation Notably, the energy consumed for sea navigation, referred to as the bunkered quantity at the sailing harbor, is partially allocated for transportation to non-EU countries, typically classified as an oil export In 2001, this bunkered quantity was estimated at 43.5 Mtep, representing approximately 14% of the overall transportation energy consumption.
The transportation sector is heavily dependent on oil, with diesel fuel accounting for 30% of railroad energy consumption, while a significant portion of electric energy is generated through oil combustion.
Road transportation predominantly relies on oil refinery products, with Italy and Holland as notable exceptions, utilizing 9% and 7% liquefied petroleum gas for traction, respectively As of 1999, the roles of coal and natural gas in this sector remain minimal, and this trend is likely to persist in the foreseeable future Overall, total consumption has stabilized in recent years.
Figure 17.6 illustrates the distribution of various fuel types utilized in transportation, measured in millions of Tjoules The increasing preference for diesel over gasoline is notable, driven by the differing retail prices and the superior combustion efficiency of diesel engines It's important to note that while fuel quantities are measured in mass, consumers purchase by volume; diesel fuel offers 12% more energy than gasoline at the same volume.
We should also notice the appearance of bio-fuels at the end on the period of time under examination.
We analyzed the energy consumption of various transportation methods, defining energy efficiency as the energy required for a unit of traffic volume Using the goods traffic unit [t×km] as a common metric, we effectively summarized both goods and passenger transportation An average mass was considered in our calculations.
70 kg for each passenger, including the transported baggage.
Accepting this questionable equivalence, we obtain the diagram of Fig.17.7.
Year Industry Transport Households Services Agricolture
Fig 17.5 Energy consumption in the European Union for most important final applications; con- sumption is measured in million of tep Source Eurostat
Fig 17.6 The figure shows the share between the different types of fuel used in transportation In this case the quantities are measured in million of Tjoule Source Eurostat
Over the past decade, road transportation has seen a 12% increase in energy efficiency, while air transportation has improved by 16% A key factor in assessing the energy efficiency of different transportation modes is the specific traction force, which is expressed as a non-dimensional ratio.
= F t mg = P max t mgd , obtained by dividing the installed maximum power of the propulsion system by the total vehicle weight and by its maximum speed.
The specific traction force can be understood as the ratio of the traction force (F t), which matches the motion resistance under steady conditions, to the vehicle's weight, effectively representing an overall friction coefficient Additionally, it can be viewed as the energy provided by the engine to transport a unit mass over a unit distance.
Year Road Railway Aircraft Navigation
Fig 17.7 Comparison of energy efficiency of different transportation means; data are elaborated from time series of the European Union
Figure 17.8 illustrates the specific traction force for various vehicle types at different maximum speeds, with each curve derived from a range of vehicles within the same family The curves on this diagram represent the lower envelope of the plotted data points.
This methodology has its limitations as it focuses solely on the top speed, which may not represent the optimal efficiency of the traction engine Furthermore, it takes into account the total weight rather than just the payload, potentially skewing the results.
On logarithmic scales, all curves align with a straight ideal line representing the optimal performance limit for isolated vehicles This line signifies the best usage conditions for each vehicle, regardless of its propulsion system.
The enlarged section of Fig 17.8 illustrates that ground vehicles, including trailers, demonstrate greater efficiency compared to isolated vehicles, as they are positioned below the limit line.
This parameter offers a quick assessment of the energy efficiency of various vehicles, while the distance from the limit lines indicates the potential for enhancement.
Fig 17.8 Specific traction force P max / mgV max as function of top speed a General diagram; b enlarged portion concerning ground vehicles
Operating Fleet
Quantity
Vehicles owned by naturalized or legal residents of Europe totalled about 378 millions in 2015; they comprise the so-called vehicleoperating fleet.
Table17.1shows a time series for private vehicles, mainly passenger cars; while Table17.2 shows public service vehicles, including commercial vehicles, light, medium and heavy duty trucks and buses.
The year 2000 figures on total transport fleet are also available for reference (source Eurostat):
• the railway fleet, included 40,000 engines and rail cars, about 76,000 cars for passenger transportation and about 500,000 freight cars;
• the navigation fleet, included about 15,000 vessels;
• the air fleet, included about 4,900 airplanes.
In 2000, the private car fleet was significant, with approximately 469 vehicles for every 1,000 citizens Over the past thirty years, this fleet has experienced a remarkable growth of around 184%, averaging an annual increase of about 3.5% Although the rate of growth has decelerated, it continues to persist.
In the United States, car density stands at 750 vehicles for every 1,000 residents, indicating a stable automotive market Recent statistics reveal that new car sales are closely aligned with the number of vehicles being retired from use.
Although this density is not inevitable for the European Union, the fleet there was still growing, and countries whose economies are growing fast are showing higher
Table 17.1 Time series of private cars in the European Union Source ACEA
Austria 4,513,421 4,584,202 4,641,308 4,694,921 4,748,048 Belgium 5,359,014 5,392,909 5,439,295 5,511,080 5,587,415 Croatia 1,518,000 1,445,220 1,433,563 1,458,149 1,489,338 Czech R 4,582,903 4,698,800 4,787,849 4,893,562 5,115,316 Denmark 2,203,191 2,240,233 2,279,792 2,334,588 2,404,091
Netherlands 8,126,000 8,142,000 8,154,000 8,192,570 8,336,414 Poland 17,871,810 18,744,412 19,389,446 20,003,863 20,723,423 Portugal 4,522,000 4,497,000 4,480,000 4,496,000 4,538,000 Romania 4,322,951 4,485,148 4,693,651 4,905,630 5,153,182 Slovakia 1,749,000 1,826,000 1,882,577 1,952,002 2,037,806 Slovenia 1,074,109 1,073,967 1,099,414 1,111,386 1,130,907 Spain 22,277,244 22,247,528 22,024,538 22,029,512 22,355,549
United Kingdom 31,362,716 31,481,823 31,917,885 32,612,782 33,542,448 European Union 241,302,219 243,350,013 243,623,290 247,704,280 252,043,348 rates, such as Greece, with 9.2%, Portugal, with 7.3%, Spain, with 6.9%, while countries with a more mature economy show lower rates, such as Denmark, with 1.8%, and Sweden, with 1.9%.
The highest car density in the year 2000 was reached in Luxemburg with 616 cars/1000 persons (corresponding to 1.62 cars per citizen), Italy with 563 cars/person and Germany with 522 cars/person.
Table 17.3 illustrates the time series of cars per 1,000 citizens in Europe, highlighting that in 1899, Italy had a ratio of 300,000 citizens for every car This ratio has consistently increased over time, with the exception of declines during the two World Wars from 1915 to 1918 and 1939 to 1945, when the total number of vehicles decreased significantly.
In 2003 this index has increased to 666 cars/1,000 citizen.
Table 17.2 Time series of public service vehicles in the European Union Source ACEA
At the same time the transportation infrastructures of the European Union can be described as follows:
• about 160,000 km of railroad network;
• about 3,250,000 km of road network, including 50,000 km of motorways;
• about 28,000 km of inland navigation routes;
• 204 airports with more than 100,000 passengers/year, with 30 of them treating75% of the total air traffic.
Table 17.3 Car density in cars per 1,000 inhabitants in the 25 Countries of the European Union
Characteristics
To gain insights into the car fleet composition, we can analyze the bar chart in Fig 17.9, which illustrates the distribution of car registrations across various market segments from 1995 to 2004.
Executive, upper medium, lower medium and small cars are considered, defined according to an overall length of more than 4.5 m, more than 4 m, more than 3.5 m and less than or equal to 3.5 m.
Year Small Lower medium Upper medium Executive Others Unknown
From 1995 to 2017, car registrations were categorized into various market segments, including executive, upper medium, lower medium, and small cars These classifications are based on vehicle lengths: executive cars exceeding 4.5 meters, upper medium cars measuring over 4 meters, lower medium cars at 3.5 meters, and small cars equal to or smaller than 3.5 meters, as defined by ACEA.
Year New PC registrations breakdown by body (%)
Saloons Estates Coupes Convertibles Monospaces Others Unknown
From 1995 to 2017, various car body types were registered, including saloons (sedans), estates, coupes, convertibles, and monospace vehicles Additionally, sport utility vehicles (SUVs) and crossovers were also classified in this data, as reported by ACEA.
The second bar chart illustrates the distribution of various body types in the automotive market Notably, there is a consistent decline in saloon cars, while niche segments such as monospace vehicles, sport utility vehicles (SUVs), and crossovers are experiencing growth Diesel engines, which became widely produced after World War II, have faced challenges due to fiscal and regulatory measures, currently holding a fleet share of approximately 24% and a market share of 44% (Source: ANFIA).
Analyzing fleet characteristics can provide insights into their expected lifespan; however, this task is challenging due to the lack of comparable historical data.
Table 17.4 illustrates the classification of car fleets in various European countries based on the number of cars per family, average ownership duration, and annual distance traveled by fuel type The average age of cars in each country is determined by calculating the average age of vehicles sold in a given year, weighted by their percentage of the total operating fleet In 2015, the average car age across 25 European countries varied from 6.2 years in Luxembourg to 17.2 years in Poland, with an overall European average of 10.7 years, as depicted in Fig 17.11 Economic factors significantly influence car age; for example, in Italy, the percentage of cars older than 10 years increased from 32.8% in 2002 to 51.6% in 2015.
As of 2002, the average age of cars in the European Union was approximately 8 years Predicting the lifespan of vehicles can be challenging, but it is reasonable to forecast an expected lifespan of around 15 years for cars and 20 years for industrial vehicles, assuming no significant changes occur.
The expected evolution of emission and passive safety regulations could promote a shorter life, increasing fleet obsolescence Macroeconomics should not be forgotten.
Table 17.4 presents data on the car fleet in several European countries, highlighting the number of cars per family, the average ownership duration, and the annual distance traveled, categorized by fuel type, as sourced from ACEA.
Country Households with a number of cars % Ownership time (years)
Second hand cars % Distance travelled (km)
Fig 17.11 The average cars age of the 25 European Countries in 2015 ranged from 6.2 years in Luxenburg to 17.2 in Poland with an average of 10.7 in Europe Source ACEA
To estimate the annual distance traveled by a vehicle, divide the traffic volume by the number of active vehicles and available spaces; however, it's important to note that most vehicles do not operate at full capacity.
In the European Union, cars contributed to a traffic volume of 4,719 Gpass×km, supported by a working fleet of approximately 252 million vehicles When considering an average occupancy of five passengers per car, this translates to an annual travel distance of around 3,800 km per vehicle.
The occupation factor, representing the ratio of occupied to available seats, is an important metric, currently measured at just 26.5% This low figure translates to an average of only 1.33 passengers per car Consequently, the average yearly distance traveled is approximately 14,000 km.
A reasonable estimate for a car’s life expectancy, therefore, should be close to 200,000 km.
Following the same process for other vehicle categories, we obtain:
• more than 400,000 km for buses;
• more than 800,000 km for long haul trucks.
Social Impact
Accidents
Road transportation, like all human activities, carries inherent risks, with a significant number of motor vehicle accidents occurring globally The economic and human toll of these incidents is substantial, making the enhancement of vehicle safety a critical social and technical priority.
Table 17.5 Death risk for some different causes, referring to the USA population in 2016
Cause Total number of fatalities One-year odds
Table 17.6 Road fatalities per 100,000 inhabitants and total road fatalities in 2013 Global data and data referred to some countries (WHO Report 2015: Data tables, (official report), Geneva: World Health Organisation, 2016)
Country Road fatalities per 100,000 inhabitants
To assess the impact of these damages, it is beneficial to examine statistics on causes of death in the United States, which may reflect trends observed in other developed nations.
These figures for 2016 are shown on Table.17.5 The number of fatalities con- nected to road transportation is second only to that caused by drug poisoning 6
6 Source The Insurance Information Institute www.iii.org.
Fig 17.12 Time series of fatalities caused by road accidents in the European Union SourceEurostat
In 2010, the World Health Organization (WHO) reported that road accidents resulted in around 1.25 million fatalities globally, accounting for one-fourth of all injury-related deaths, while approximately 50 million individuals sustained injuries in traffic incidents Additionally, a study by the American Automobile Association (AAA) estimated that car crashes impose an annual economic burden of $300 billion on the United States.
In the European Union, transportation accidents caused 50 fatalities per million inhabitants in the year 2016; about 5.2 fatality/Gpass×km or 100 fatalities per million passenger car.
Figure17.12shows a summary of this worrying situation.
Despite the rise in traffic volume, total fatalities are fortunately on the decline, thanks to enhanced driving education, improvements in infrastructure, and increased vehicle passive safety resulting from stringent regulations.
The total road fatalities occurred about 59% on cars, 18% on motorcycles and 10% on bicycles, as shown on the pie chart in Fig.17.13.
Referring fatalities to different passenger traffic volumes, we obtain the following mortality rates 7 :
• 9.5×10 − 9 deaths/pass×km, for road transportation (more precisely: 0.7×10 − 9 deaths/pass×km for buses, 7×10 − 9 deaths/pass×km for cars, 13.8×10 − 9 deaths/pass×km for motorcycles, 54×10 − 9 deaths/pass×km for bicycles and
64×10 − 9 deaths/pass×km for pedestrians);
• 0.35×10 −9 deaths/pass×km, for railway transportation;
• 0.35×10 −9 deaths/pass×km, for air transportation.
7 Source European Transport Safety Council, data calculated for year 2002.
Fig 17.13 Pie chart showing the brakedown of fatalities according to the different kind of vehicles
Air transportation presents significant challenges, particularly regarding accidents that take place within the European Union or involve European airlines, regardless of their location It is crucial to focus on European citizens and all individuals affected by these incidents.
Most accidents tend to occur in proximity to airports, and varying counting methods yield different conclusions about their frequency Additionally, these incidents, although infrequent, fluctuate over time, making it challenging to derive meaningful averages.
The reported figure refers to all accidents occurring in 2002 within the borders of the European Union.
Returning to road transportation, accident severity has also decreased, as we can conclude by examining Fig.17.14 showing the time series of the ratios between non-fatal injuries and deaths.
Emissions
The combustion of oil refinery products and road traffic generates significant pollutants that pose serious risks to public health.
• non-methane organic compounds (NMOC);
Recently, additional gases have been recognized for their role in the greenhouse effect While these gases are not directly harmful, they are classified as greenhouse gases (GHG) due to their contribution to environmental warming.
Fig 17.14 Time series of the ratio between non-fatal injuries and deaths due to road accidents in the European Union Source Eurostat
Carbon monoxide (CO) is a flavorless, colorless and poisonous gas; if exchanged with blood hemoglobin, in the lungs, it impairs the quantity of oxygen delivered to body organs and tissues.
Gasoline engine combustion is a major source of carbon monoxide (CO) emissions, primarily due to incomplete combustion of organic fuels resulting from insufficient oxygen This issue extends beyond cars to include other gasoline engines, such as motorcycles, as well as diesel engines, incinerators, and residential heating systems.
Figure17.15shows a CO breakdown by source as estimated for the European Union in the year 2000.
The ongoing decline in these values is primarily attributed to the shift from wood-burning furnaces to natural gas, alongside stricter regulations on vehicle emissions, which have lowered permissible limits for gasoline engine cars from 4.05 g/km.
1992, to 1 g/km from 2005; the introduction of catalysts in 1992 had already reduced
CO emission by ten times.
Nitrogen oxides (NOx), comprising nitric oxide (NO) and nitrogen dioxide (NO2), are produced when atmospheric nitrogen and oxygen combine during high-temperature combustion processes Consequently, more efficient combustion leads to increased nitrogen oxide formation This creates a conflict between reducing fuel consumption and CO2 emissions while also aiming to lower nitrogen oxide emissions.
A second major source of NO x is nitrate salts used in agriculture, which produce acids emitting nitrogen in the presence of water.
Fig 17.15 CO breakdown by source for the European Union for the year 2000 Source ACEA
Fig 17.16 NO x breakdown by source for the European Union in the year 2000 Source ACEA
Nitrogen dioxide (NO2) irritates the lungs and can reduce their resistance to infec- tion, with increased risk for bronchitis and pneumonia.
Contributions to this pollutant are many, as shown in Fig.17.16, again based on the year 2000.
Nitrogen oxides (NOx) and non-methane organic compounds (NMOC) are key precursors in complex chemical reactions that lead to the formation of ozone (O3) in the lower atmosphere, which is harmful to human health.
Anthropogenic sources of nitrogen oxides (NOx) have significantly decreased due to stricter vehicle regulations, which have lowered emission limits from 0.78 g/km in 1992 to 0.06 g/km for petrol and 0.08 g/km for diesel vehicles by 2014.
Fig 17.17 NMHC breakdown by source, in the European Union in the year 2000 Source ACEA
Figure17.17shows a similar diagram for NMOC; the evaporation of fuels and solvents is a major contributor.
From 1992 to 2014, vehicle regulations have significantly lowered nitrogen monoxide (NMOC) emissions from gasoline engines, decreasing levels from 0.66 g/km to 0.068 g/km Particulate matter, a harmful mixture of particles of varying sizes, poses health risks, damages materials, and reduces visibility These particles are classified by their average diameter and are suspended in the atmosphere, where they settle slowly, with the most harmful particulates being those that remain airborne.
PM-10 indicates particles smaller than 10àm, while PM-2,5 refers to sizes smaller than 2,5àm.
The smaller the particle the greater the risk for human health Extended exposure to these particles affects breathing, can worsen existing pulmonary diseases and increases cancer risk.
In addition to combustion products, airborne particles comprise dust, ash, smoke, and droplets If not removed by rain or other methods, ground-level powders can become airborne again through natural winds or the movement of vehicles.
PM also follows a decreasing trend; vehicle regulations have reduced levels from 0.08 to 0.005 g/km in the period 1996–2014.
Figure17.18shows a breakdown of the main sources of PM-10.
The greenhouse effect is driven by a range of gases, specifically six key chemical compounds recognized in the Kyoto Protocol: carbon dioxide (CO2), methane (CH4), nitrogen dioxide (NO2), hydrofluorocarbons (HFC), perfluorocarbons (PFC), and sulfur hexafluoride (SF6).
All these gasses, if diffused into the atmosphere, limit infrared radiation, con- tributing to an increase in the atmosphere’s average temperature.
They are measured according to their heating potential, which is reported as CO2 equivalent; their quantity is multiplied by weights p i , which express the carbon dioxide equivalent.
Fig 17.18 PM-10 particulate breakdown by source in the European Union in the year 2000 Source
Fig 17.19 Greenhouse gasses broken down by source, measured as CO 2 equivalents Source
The weights of various greenhouse gases (GHGs) are as follows: pCO2 = 1, pCH4 = 25, pNO2 = 210, and pSF6 = 900 Hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs) comprise two significant families of gases, each with distinct weights A pie chart illustrates the GHG emissions breakdown by source, highlighting that emissions are closely linked to population size, with France, Germany, Italy, and the United Kingdom contributing over 50% of Europe's total To mitigate these emissions, a reduction in fossil fuel combustion is essential Consequently, European Union legislation has established mandatory reduction targets for new vehicles, as cars are responsible for approximately 12% of total CO2 emissions.
8 These data are unfortunately not consistent with the others, because they refer to the EuropeanUnion as extended to 25 countries.
The 2015 and 2021 targets represent reductions of 18% and 40% respectively, compared with the 2007 fleet average emission figure of 158.7 g/km (car emission weighted on sales volume).
The average emissions level of a new car sold in 2017 was 118.5 g/km, significantly below the 2015 target of 130 g/km.
As of 2020, the fleet average emissions have been established at 95 g/km, translating to an average fuel consumption of approximately 4.1 liters per 100 kilometers for petrol and 3.6 liters per 100 kilometers for diesel vehicles.
Electric vehicles, we will introduce in a following chapter, are considered by the public opinion as the final solution for solving all emission problems.
Electric cars significantly reduce emissions of CO, NMOC, NOx, and PM, as power station emissions can be managed more effectively than those from car exhaust systems Additionally, electric vehicles are inherently less polluting due to their low-pressure combustion process However, it is important to note that the reduction of CO2 emissions is not as straightforward, as there is currently no cost-effective after-treatment technology available for this pollutant.
Figure17.20shows the CO2content of electric energy at the wall socket in the Countries of the European Union In the Union there are on one side Countries as
Fig 17.20 CO 2 content of electric energy at the wall socket in the Countries of the European Union in 2009 Source European Environment Agency
Fig 17.21 Diagram of SO 2 concentration and smoke, as functions of time, in London
France, Norway, and Sweden exhibit low carbon emissions due to their extensive use of nuclear and hydroelectric power stations, while countries like Poland, Germany, and the United Kingdom have higher emissions due to a significant reliance on petroleum power plants The average carbon emission across the European Union stands at approximately 400 g/kWh.
An electric mid-size car with an energy consumption of 25 kWh per 100 km emits approximately 125 g/km of CO2, which is only marginally better than the 2015 emissions target for traditional internal combustion engine vehicles.
Finally we should remember that air pollution is a phenomenon preceding devel- opment of the automobile, especially in urban environments and it has been declining for many years.
If public perception has increased, this is due more to the evolution of laws, than the problem per se.
Economic Figures
The turnover generated by the ACEA manufacturers represents 6.8% of Europe Gross Domestic Product.
The automobile industry significantly impacts the economy, sustaining a large supply chain and a variety of business services It employs approximately 13.3 million individuals, accounting for 6.1% of the European workforce.
The 3.4 million jobs in automotive manufacturing represent 11.3% of European manufacturing employment Vehicle manufacturing is a strategic industry in Europe, where 19.6 million cars, vans, trucks and buses are manufactured per year.
Automobile manufacturers operate some 304 vehicle assembly and production plants in 27 countries across Europe.
The European auto industry is a global player, delivering quality products around the world, and bringing in a 90.3 billion Euro trade surplus.
Motor vehicles account for 413 billion Euro in tax contributions in the EU15 Countries alone.
The auto industry is the largest private investor in R&D in Europe, with almost
In 2017, over 8,700 patents were granted to the automotive sector by the EuropeanPatent office.
System Design
Functions Perceived by Customers
Let us consider all functions performed by the vehicle, with particular reference to automobiles.
Vehicle functions can be defined as the categories by which the customer rates vehicle performance.
A complete list of functions, probably to be expanded in the future, can include the following:
Each function of the vehicle is defined by specific qualitative and quantitative requirements essential for its proper performance We will briefly outline these critical attributes.
The primary function discussed is appearance, which refers to the product's appeal to customers Although this topic may extend beyond the book's scope, essential requirements include the product's shape, volume, materials, and intricate details.
The chassis plays a subtle yet significant role in a vehicle's performance, influenced by factors such as tire and wheel size, which also affect its appearance Additionally, the engine's layout, including an open hood and the design of hood shapes and ventilation openings, further enhances the overall functionality of the car.
Roominess, or, from a designer point of view, the use of space, is important, because it embodies the primary objective of carrying people and goods.
Customers prioritize the efficient use of space in vehicles rather than expecting unlimited room, particularly based on the car class they are considering The layout of car components should minimize any encroachment into the passenger area, as space occupied by these components cannot be utilized for passengers This focus on optimizing space is why we dedicated significant attention to the design of transmission and suspension bulk in our initial volume.
Key requirements for body design include spaciousness and the ability to organize small items effectively Additionally, adaptability features like tilting or removable seats are essential, allowing customers to customize the car's interior to meet various transportation needs.
Carergonomicscan be defined as the ability to minimize the physical activity required by a given operation while using the car Within this function, we usually
18.1 System Design 39 include the pleasure of driving the car, including the many sensations the customer feels while driving.
The requirements of this function again involve the car body and include:
• ease of entering and exiting the car for driver and passengers, of opening and closing doors, the glove compartment, hood, trunk, etc.;
• ease of identifying and reaching the most important controls with minimal reach;
• comfort of the driver’s posture;
• ease of loading and unloading transported goods.
Chassis design is significantly influenced by the functional requirements of car controls, including the steering wheel, gear shift stick, clutch, and brake pedals Key factors include the operating force needed, the positioning of these controls, and the tactile feedback experienced during use Effective controls must minimize driver fatigue while providing clear feedback to ensure successful maneuver execution.
We commented aboutclimate comfortin our example In this case as well, the related requirements affect body design and, partially, the engine.
Thedynamic comfortfunction is evaluated by the ability to suppress all acoustic and vibration nuisances from outside (road pavement and other vehicles) and from inside (engine operation and component vibration).
The related requirements involve almost all vehicle components, as they partici- pate as sources and potential transmitters of such disturbances.
Noise and vibration in vehicles provide essential information for both drivers and passengers A completely silent vehicle, devoid of vibrations, could pose safety risks, as evidenced by experiences with active noise suppression systems Furthermore, specific sounds are characteristic of certain vehicle types, such as the distinctive noise of sports cars.
The target is not total suppression but an acoustic environment compliant with customer expectations.
Filtering of component vibration is a task usually assigned to the body system, while filtering noise and vibrations from the road is usually assigned to the wheels and suspension.
Filtering powertrain noise (engine operation) involves powertrain suspension and the intake and exhaust system.
Unbalanced specifications are linked to potential vibration sources, while the dynamic performance function encompasses measurable requirements like top speed, gradeability, acceleration, and pick-up More challenging to assess are drivability and fuel economy These requirements pertain to all chassis components, extending from the engine to the body, and generally apply to the entire vehicle.
Handling functions refer to a vehicle's responsiveness to driver inputs when adjusting speed or direction, utilizing controls like the steering wheel, brakes, and accelerator Key requirements for effective handling encompass not only the suspension, tires, steering mechanism, and brakes but also the engine and transmission Additionally, the overall properties of inertia, including mass and momentum, play a crucial role in determining a vehicle's handling capabilities.
Thesafetyfunction is usually classified in three ways:
1 preventive safety, such as the ability of the vehicle to keep the driver constantly updated on corrective maneuvers to be undertaken; a typical example of this category includes not only outside visibility, visibility of the main instruments (i.e., speedometer, outside thermometer, etc.) but also car trim variations;
2 active safety, such as the ability of the vehicle to react to driver inputs with a response that should be immediate, stable and proportional to the action, while avoiding obstacles or dangerous situations;
3 passive safety, such as the ability to limit, when a collision is unavoidable, the severity of injuries to car occupants, to pedestrians or to passengers of other cars, involved in the collision.
Safety can never be absolute; however, it is essential to set requirements for the most statistically significant scenarios Homologation requirements play a crucial role in this strategy, alongside the technical policies of manufacturers Recently, limitations on repair costs for low-speed collisions have been introduced in the realm of passive safety.
Vehicle safety encompasses all key components, with the body playing a crucial role in both preventive safety—through features like visibility and lighting—and passive safety, which includes structural integrity and restraint systems Additionally, the chassis must meet active safety standards related to suspension, brakes, and tires, while also adhering to passive safety regulations that prevent intrusion into the passenger compartment during collisions.
The engine system is involved in passive safety as far as fuel spills after crashes and consequent fire hazards are concerned.
Aging resistance in vehicle systems refers to the capability of components to retain their functionality or minimize degradation over time, ensuring reliability This essential characteristic encompasses all vehicle parts, particularly focusing on chassis components.
Chassis System Design
We have seen that the automotive chassis contributes to the following vehicle func- tions:
The dynamic performance of a vehicle is influenced by several key components, including the engine and transmission, which determine the available power Additionally, factors such as aerodynamic resistance from the body, rolling resistance from the tires, mechanical efficiency of the transmission, and the vehicle's mass properties all play a crucial role in how effectively power is absorbed during operation.
The suspension and steering system geometry, brake design, and tire elasticity significantly impact handling and active safety, while the transmission affects the relationship between cornering and traction forces Additionally, chassis control systems are crucial for optimizing vehicle performance.
Ride comfort is significantly impacted by vibrations from tire-ground contact, which are influenced by the vehicle's suspension geometry and the elastic and damping characteristics of springs, bushings, and shock absorbers Additionally, the vertical properties of tires play a crucial role in determining overall ride quality.
Acoustic comfort, on the other hand, requires a notable development of our knowl- edge of body structure and trim For this reason, this function is usually studied in body design.
Ergonomics in vehicle design focuses on the chassis, specifically the steering system, brakes, and transmission, including the clutch and shift stick Additionally, control systems enhance these functions with power assistance and automatic transmissions, improving overall user experience and vehicle performance.
Passive safety focuses on the design of the chassis and the prevention of component intrusion into the passenger compartment As most vehicles feature a unified shell that combines both chassis and body structures, this aspect is typically examined within the context of body design.
This book focuses on design methods for chassis components, aiming to ensure they effectively meet essential functions within the vehicle system.
The effectiveness of these methods may seem somewhat inadequate, as we will outline how to assess the functions an assigned vehicle can perform and identify the components that influence these functions However, we will not specify how these components should be configured to achieve the desired performance levels This issue can only be addressed retrospectively, whereas a proactive approach would be preferable.
This qualification is relevant to all design courses, as design involves defining a product that does not yet exist Essentially, the focus is on assessing whether an existing product can effectively fulfill its intended function.
The designer's role involves formulating a hypothesis and testing its outcomes; any deviation from the goal prompts the creation of a new hypothesis for further verification While the designer's efficiency increases with a more accurate initial hypothesis, the design process ultimately remains one of trial and error.
A technical specification is challenging to define since the ultimate assessment of a product is determined by the customer rather than the designer Customer evaluations can be difficult to articulate clearly, as they are often shaped by intangible factors and competing market options that may not be apparent at the start of the development process.
Technical specifications are established through a two-part process: target setting and target deployment The target setting phase involves defining objectives for each function as perceived by the customer, emphasizing the importance of using objective measurements over subjective judgments While this approach is straightforward for quantifiable functions such as top speed, acceleration, and gradeability, it becomes challenging for more subjective aspects like handling, which rely on personal feelings.
We will see in the following paragraphs how subjective feelings can be trans- formed into objective measurements.
In the next phase of target deployment, vehicle subsystems will be identified based on their functions, with tentative specifications established The adequacy of these specifications will be verified against the targets, correcting any discrepancies Verification may involve using mathematical models of the vehicle and, in some instances, constructing and testing simplified prototypes, known as mule cars, to validate complex subsystems.
Objective Requirements
Dynamic Performance
For this kind of test it is necessary, for safety reasons, to use test tracks closed to public traffic.
For accurate speed and acceleration testing, it is essential to conduct these evaluations on a long, flat, and straight road Additionally, a launch ramp should be utilized to ensure the vehicle can achieve its maximum speed prior to measurement.
Sufficiently long constant slope roads, at different inclination angles, should be available for gradeability tests.
Loop tracks are designed to simulate meaningful road trips for vehicle testing By adhering to specific guidelines during driving, these tracks enable accurate measurement of average speeds and fuel consumption, providing data that closely resembles real-world values.
Engine performance is affected by air density and humidity, making climate conditions crucial during tests Ideal testing conditions include an outdoor temperature between 10°C and 30°C, with no wind or rain.
Roller benches serve as an effective alternative to traditional test tracks, especially when variable climate conditions limit availability These benches enable the simulation of vehicle driving resistance through electronic control of electric brakes, allowing for precise testing at assigned speed time histories This method is particularly beneficial for accurately measuring fuel consumption.
A roller bench, when contained in a pressure and temperature controlled chamber, allows dynamic performance to be measured at temperature and altitude conditions different from those available outside.
Test vehicles require a minimum driving distance of approximately 5,000 km post-assembly to ensure the stabilization of mechanical frictions and tire rolling resistance, as these factors can vary based on surface wear.
To ensure optimal performance, it is essential to manage the transported weight within a statistically significant range, typically testing with two passengers (including the driver) and 20 kg of luggage For industrial and commercial vehicles, performance assessments are conducted under full load conditions.
The testing instruments are straightforward, utilizing optical devices to activate stopwatches for measuring driving times, while the distance traveled is calculated based on the devices' positions along the track Fuel consumption is monitored using volumetric flow meters on the engine's fuel feed line, accounting for recycled flow back to the fuel reservoir, and occasionally employing an auxiliary tank that is weighed before and after the test.
The best-known dynamic performance istop speed, which is the maximum vehicle speed on a flat road, after a reasonably long launch ramp.
Acceleration is typically defined as the time taken to reach a specific speed, commonly 100 km/h (60 mph), from a complete stop while using the gearbox at full throttle It can also be measured by the time required to cover a set distance, such as 1 km or 1/4 mile, under the same conditions To achieve accurate results, this test should be conducted multiple times with a manual gearbox, allowing the driver to determine the optimal control strategy, as both start-up and shift times significantly impact the final outcome.
Pick-up time refers to the duration required for a vehicle to accelerate from a set initial speed, such as 50, 60, 70, or 80 km/h, to a final speed of 100 km/h, all while maintaining full throttle and without shifting gears Typically, this is measured in the top gear or the gear that allows for maximum speed Additionally, the distance traveled during this acceleration can also serve as a metric for evaluating performance.
Gradeability refers to the steepest incline a vehicle can ascend and maintain a steady speed without clutch slippage This measurement is determined based on the elevation difference between the two endpoints of a test track, divided by the horizontal distance of the track, representing the tangent of the longitudinal slope angle (α).
Manufacturers utilize reference loop drives on both closed tracks and open roads to assess road performance under controlled conditions, measuring average speed or driving time during these evaluations.
Rising traffic congestion has shifted customer focus from the performance of intensive gearbox use to the importance of low-speed pick-up time Recent statistical surveys indicate that subjective perceptions of performance increasingly favor this metric during short test distances.
The growing trend emphasizes the significance of low-speed engine torque (1,500−2,500 rpm) in relation to maximum power, highlighting its role in enhancing drivability as a key aspect of vehicle dynamic performance.
Drivability can be defined as the vehicle’s ability to increase or decrease its traction force quickly, without fluctuation around the final desired value.
At the beginning of the test, the throttle pedal is depressed or released starting from a condition corresponding to the initial steady state reference speed.
Drivability is assessed by analyzing the car speed over time following accelerator pedal input or by measuring longitudinal vehicle acceleration A key objective evaluation metric is the number of peaks in the speed diagram before reaching the asymptotic value.
Vehicle drivability is affected by engine torque oscillations caused by flow transients in the intake and exhaust systems, as well as the elastic torsional stiffness of the driveline, which includes components from the clutch to the tires Additionally, the elasticity of the powertrain and suspension mounts plays a crucial role in overall drivability.
Handling and Active Safety
Handling tests are closely related to active safety tests, as they both assess vehicle performance under various conditions These tests present unique challenges due to the numerous on-road maneuvers involved, which are further complicated by varying road surfaces and environmental factors.
Many manufacturers have implemented standardized basic maneuvers, primarily governed by ISO guidelines, which focus on the execution of these maneuvers rather than establishing output reference values The test track, typically a flat square that can be flooded under controlled conditions, features marked courses for vehicles to follow, ensuring that the repercussions of errors are minimal.
Cars are often equipped with roll-over protection provided by additional wheels that contact the ground at high roll angles.
Vehicle instruments must be sophisticated because they have to measure dynamic values for the vehicle; the essential ones include:
For the definition of each see the Part Four of this volume.
A fixed reference system is essential for determining values using instruments mounted on the vehicle To achieve this, an inertial platform is employed to measure the six components of rotation and displacement of the vehicle's sprung mass in relation to the ground.
In many tests a particular steering wheel able to measure steering angle and torque is used.
Tests can be categorized into open-loop and closed-loop systems based on the driver's involvement during maneuvers In open-loop tests, the driver follows a predetermined procedure using vehicle controls such as the steering wheel, brakes, and accelerator, without regard to the outcome Conversely, closed-loop tests require the driver to actively use the controls to achieve a specific goal, such as navigating a course at maximum speed.
The simplest open-loop maneuver is the steering pad (ISO 4138), where the vehicle is driven around a circle at constant speed.
This is an open-loop maneuver because the controls are blocked during the test period, to guarantee a steady state motion.
Three different methods are considered depending on the skill of the driver, that are substantially equivalent in result; these are:
Since these are the three independent variables that define motion, their test results can determine the remaining variables.
A typical curvature radius ranges from 40 to 100 meters, and it is essential to conduct tests that yield varying lateral acceleration values Beginning with a low lateral acceleration is crucial for accurately measuring the Ackermann steering wheel angle.
This test evaluates a vehicle's steering index and determines the roll angle in relation to lateral acceleration, enabling the identification of the maximum permissible lateral acceleration through multiple trials.
We refer again to the fourth part of this volume for a definition of the parameters involved in this test.
The lateral transient test (ISO 7401) is commonly used to assess vehicle stability during curve entry and the realignment of the steering wheel upon exit The vehicle is stabilized on a straight road at a speed of 100 km/h, or at alternative speeds if preferred In this test, the steering wheel is abruptly turned to a predetermined angle, facilitated by a steering wheel stop The accelerator pedal position remains unchanged while the steering wheel is held in the turned position for a designated duration.
Key evaluation parameters include the gradient of lateral acceleration and yaw speed in relation to the steering wheel angle, the delay time between the peaks of steering wheel angle and yaw speed, and the occurrence of overshoots in the yaw speed diagram, where the yaw speed peak exceeds the asymptotic value.
A variant of this maneuver is the application of a sinusoidal steering wheel input applying, as input:
• sinusoidal function, at different frequencies.
The complexity of this test is evident despite the schematic simplicity of this transient motion between straight and curved steady-state motions.
The accelerator pedal release maneuver (ISO 9816) examines how vehicles respond when the accelerator is released while navigating a curve, simulating the potential consequences of driving at excessive speeds.
It is possible to test vehicle stability and measure deviation from the original path.This test can be performed at the end of the steering pad test.
Two different methods are available.
To investigate the impact of lateral acceleration, maintain a constant course by stabilizing the vehicle on the designated curvature radius before easing off the accelerator pedal; this allows for an increase in steady-state speed as necessary.
• At constant speed, stabilizing at a certain speed on decreasing curvature radii.
The test results highlight the relationship between the steering index, lateral acceleration, and the changing cornering stiffness of tires, which are influenced by the immediate traction changes during braking Additionally, the engine exhibits a braking effect that intensifies with higher initial rotation speeds, while the transient motion is influenced by the chosen gear ratio.
During this open-loop test the steering wheel must be locked.
The evaluation parameters remain consistent with the previous test, now incorporating longitudinal acceleration Due to the steering wheel being locked, a deviation from the initial course occurs upon releasing the accelerator Typically, vehicles are engineered to slightly realign their path after the transient phase, ensuring a smooth transition without significant disruption to the original trajectory.
The braking in a curve test (ISO 7975) has been developed to enhance stability by incorporating brake application into the procedure, while the steering wheel remains locked during the test.
In addition to the previous test parameters, braking fluid pressure is introduced, which may lead to significant deviations from the initial trajectory The test is conducted with increasing longitudinal accelerations until either one of the wheels locks or the ABS system activates.
An important open-loop maneuver is thesteering wheel release(ISO 17288); the purpose of this test is to establish the vehicle’s ability to return to a straight path after a curve.
The vehicle is stabilized at a speed of 100 km/h on a steering pad, with a path curvature designed to maintain a lateral acceleration of approximately 1 m/s² During the test, the steering wheel is allowed to turn freely due to the forces acting on the tire contact points, while the accelerator pedal remains unchanged Key parameters such as steering angle and lateral acceleration are recorded, and the observed damped oscillations in the steering wheel and lateral acceleration are analyzed, using the damping factors from the time histories to evaluate these transient motions.
Side wind sensitivity tests for cars (ISO 12021) and for industrial vehicles (ISO
14793) are also available; for these vehicles specific tests can be used to examine the effect of trailers.
Dynamic Comfort
Comfort is correlated to passenger unease caused by vibrations between 1 and 100 Hz in frequency; higher frequency vibrations correlate solely with purely acoustic dis- comfort.
Vibrations from road obstacles and hollows are mitigated by the elastic and damping characteristics of tires, suspensions, and seats These components significantly influence the impact of powertrain mass vibrations caused by the road surface, as well as the body vibrations, either enhancing or reducing their effects based on the specific vibration modes.
Comfort tests are conducted on controlled tracks that simulate typical road surfaces a vehicle may face To ensure consistent and repeatable results, these tracks must be maintained to specific standards.
Controlling and recording ambient temperature is crucial due to its significant impact on the elastic and damping properties of elastomers, commonly used in mechanical components that connect the ground profile with passengers Additionally, temperature greatly affects the oil viscosity of shock absorbers.
Measurements to evaluate include the acceleration of components in contact with the human body, such as the floor, seat, and steering wheel Additional accelerometers can be positioned throughout the mechanical system to enhance test accuracy and facilitate diagnostic assessments.
Accelerations must be measured along the vehicle's three primary axes, particularly when significant components are aligned with the z and x axes Additionally, accurately measuring vehicle speed is crucial, as it, along with the road profile, helps validate the test results.
Four profiles exist for elementary tests that replicate the most common road defects.
A well-maintained motorway features a smooth, flat surface with spacing between peaks and hollows that exceeds the vehicle wheelbase At speeds of 100–120 km/h, this spacing can resonate with the natural vertical frequency of both the powertrain and vehicle suspension This type of road is also utilized for detecting and analyzing vibrations caused by tire shape and any defects present in the tires.
Poorly maintained suburban roads feature closely spaced hollows, varying pit sizes, patches, and ruptures in the wear layer, as illustrated in Fig 18.2 These defects produce a broader range of frequencies that can trigger the natural vibration modes of both sprung and unsprung masses Ensuring comfort during travel is essential for customer satisfaction, particularly because these road imperfections are prevalent.
Stone block pavement remains prevalent in urban centers due to its aesthetic appeal and resistance to ice damage, making it a standard reference for urban environments Additionally, it is linked to lower vehicle speeds compared to previous pavement tests.
The surface's characteristics result in a broad wavelength spectrum, ranging from centimeters to several meters This wide spectrum excites all comfort frequencies, impacting various suspension components and the overall car structure.
The comfort tests catalog typically features a single-step obstacle that simulates the experience of crossing a curb or railway This obstacle is designed as a rectangular steel bar placed across a flat tarmac road.
Fig 18.2 Typical defects of suburban and urban roads, relevant to vehicle comfort; at left a patched tarmac; at right a stone block pavement
18.2 Objective Requirements 53 generates a force pulse on the wheels and involves a wide range of frequencies, with vibrations along thezandxaxis.
Ergonomics
The ergonomic design of a vehicle's chassis is significantly affected by the placement of controls and the effort needed to operate them Key controls such as the steering wheel, brake and clutch pedals, gear shift stick, and parking brake play a crucial role in ensuring driver comfort and functionality.
The growing trend of expanding passenger compartments emphasizes the pedal board as a crucial element in assessing car habitability Situated within the passenger area, the pedal board is influenced by several key factors.
• front wheel well: its dimensions are determined by the front wheel steering enve- lope and by the suspension stroke; this volume should also take snow chains into account;
• floor tunnel, for the transmission shaft on rear wheel driven cars and for the exhaust pipe in front wheel driven cars;
• minimum clearance from the ground;
• firewall, separating the passenger compartment from the engine, which is also used to attach the pedal board.
To maximize space for drivers and passengers, it's essential to position the pedal board as far forward as possible However, this forward placement is constrained by the powertrain and steering box, while lateral positioning is limited by the floor tunnel and wheel well These spatial restrictions are particularly significant in narrow vehicles.
The accelerator pedal remains engaged with the driver's right foot at all times, except during braking It should be manipulated with minimal force and utmost precision, necessitating a side rest for the foot to prevent disruption from vertical vibrations.
The accelerator pedal stroke should be about 50–60 mm.
The heel point serves as a crucial reference point for positioning the accelerator pedal, determined by the most rearward position of the driver's foot when resting on the floor, as dictated by projected comfort angles.
To avoid excess contact between shoe and pedal, the relative motions of these two parts should be minimized.
The shoe sole's direction changes due to pedal motion, with a fixed hinge point ensuring minimal slip between the pedal and shoe This optimal no-slip condition is best achieved at mid-stroke, the position most commonly used To further reduce slip in other pedal positions, a curved design can be implemented.
The brake pedal can be operated by relevant forces and stroke precision is not very important.
According to regulatory standards, the control force must not be higher than
500 N, but it is suggested that this control be designed to limit the maximum pedal force below 200–250 N, using the power assistance system.
To exert control forces easily, it is assumed that the driver’s foot is angled on the floor to reduce the torque on the heel.
This kind of operation is allowed for emergency braking only, while for ordinary braking, the pedal is depressed in the same way as the accelerator.
The clutch pedal can also be operated in two ways, according to design choices and driver’s habits:
• with the heel on the floor;
• with the foot at a higher position for the first part of the pedal stroke, and resting on the floor at the end of the stroke (clutch fully disengaged).
The first mode is used for precision modulation, as for starting up on a grade In this phase the pedal stroke is limited.
Because the force on the pedal should stay below 100 N, the foot position could be advanced without negative consequences on heel torque.
In most pedal boards, the hinge axes of the accelerator and brake pedals differ, whereas the clutch and brake pedals share the same axis To accommodate varying strokes for the clutch and brake pedals, the clutch pedal can be positioned higher when at rest.
To avoid interference with other pedals when depressing a pedal quickly, the distance between pedal centers should be as high as the sole width, not less than
Steering wheel positioning is more complex and must take into account:
To ensure optimal functionality of the pedals, it is essential to maintain a minimum relative distance of approximately 650 mm between the highest pedal in its resting position and the lower surface of the steering wheel.
• a comfortable inclination for the steering wheel of about 30 ◦ –35 ◦ ;
• a rotation axis placed at least 300 mm from the middle of the vehicle, to avoid interference with the front passenger during steering;
• interference with the driver’s leg while entering and exiting the car.
All decisions on control positions should be taken at the same time the body is outlined Because of this, such decisions are rarely made by chassis designers.
A relevant indicator of steering wheel ergonomics is the force needed to turn the steering wheel at low speed.
This evaluation should be made by executing steering cycles, at low car speed (about 5–7 km/h), from stop to stop; steering wheel rotation speed should be between
The output of this test reveals the hysteresis cycle of the steering wheel, as explained in the first volume, in the section on power steering.
When electric by-wire transmissions have totally replaced mechanical controls,there will be much more freedom to position these controls than was possible earlier.
Major future developments include the possibilities of:
• using joy-sticks or other devices, instead of the traditional steering wheel;
• integrating other functions such as shift, brake and clutch control in the steering control;
• mounting the steering control on moving boards, to enhance vehicle accessibility and to allow driving from either side;
• personalizing controls depending on user needs, to allow disabled people, for example, to drive more easily.
Other information about controls is reported in the first volume.