There is also evidence that stringent renewal procedures and demanding medical examinations at renewal reduce the level of car driving licenses among older people. France, The Netherlands, and the United Kingdom have the highest level of driving license holding by people aged 65+, which has direct implications for the independent mobility of older people. Reduced mobility also has safety implications: in about half the European countries for which road accident fatality data have been analyzed, people aged 65+ are at greater risk of death as a pedestrian than as a car driver.

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This is a review paper of experimental measurements of the effects of road and tire characteristics on the rolling resistance and fuel consumption of cars, goods vehicles, and buses. The rolling resistance of tires has been reduced by improved design and can be reduced in use by higher inflation pressures and, for goods vehicles, by the use of wide single tires in place of duals. For heavy vehicles, higher inflation pressures and wide single tires increase road wear. On paved roads, rolling resistance and fuel consumption is increased separately by the surface macrotexture and the profile unevenness. These effects are additive and over the range of conditions found on European roads can each increase car fuel consumption by about 5% Unevenness can increase goods vehicle fuel consumption by up to 10% On unpaved roads in developing countries, fuel consumption of goods vehicles and buses is increased by 15 to 20% over that on paved roads. In addition, loose material on the road surface further increases fuel consumption.

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Heavy goods vehicles apply higher than expected loads to road pavements because of dynamic bouncing. The Transport Research Laboratory has measured these loads for a variety of steel, rubber and air suspensions on their research track and on public highways. Bouncing of goods vehicles in motion causes dynamic pavement loads with standard deviations that are typically 10-30% of static loads, depending on the suspension type and road roughness. Tests indicate clearly how much these dynamic loads can be reduced by suitable choice of suspension. An estimate is made of the amount that road wear could be reduced if all goods vehicles used the best of current suspensions. Some measurements have been made of the effect of different suspensions on the peak dynamic axle loads on bridges. Work is in progress to develop simple instrumentation that can be fitted quickly to vehicles for measur ing dynamic wheel loads, and test procedures to enable the road-friendliness of different types of suspension to be assessed. The European communities have defined road-friendliness in terms of suspension frequency and damping. Experimental evidence linking dynamic loads on roads to the parametric characteristics of suspensions is described. Other potential procedures for rating suspensions are discussed.