Page - 1 - in Maximum Tire-Road Friction Coefficient Estimation

1. Introduction In the year 2000, more than 40,000 people died and 1.7 million people were injured in roadtrafficintheEuropeanUnion. Thesenumbersandtherelatedsocietal consequences have led the European Commission to define its long term zero-vision, setting the goal of reducing all fatalities to a value close to zero by 2050, [Off01]. In 2009, the European Commission resolved to halve the number of fatalities by 2020 as an additional measure, [Off11]. To reach these ambitious goals, countermeasures are necessary that focus on the complex interactions between driver, vehicle and environment and also consider the different levels of traffic safety, see Sections 1.1 and 1.2. To develop countermeasures, traffic research is necessary. 1.1. Significance of friction potential for traffic safety In theyear2011, approx. 9%ofall accidents involvingpersonal injury inGermanywere relatedto the roadsurfaceand lightingconditions, [Deu12]. Poor roadconditions leadto a reduced maximum coefficient of friction between tire and road, which is referred to as friction potential. In most cases, road surface conditions themselves were not the main accident cause. Improper driving, e.g. exceeding speed limits or failing to observe the priority rules in traffic, and improper pedestrian behaviour were identified as the cause in 90 % of accidents. In combination with the aformentioned cases of reduced friction potential, these improper driving behaviours could often not be corrected in time and resulted in accidents. In comparison, technical or maintenance faults of vehicles were responsible for only 0.7 % of accidents according to the same statistical source, [Deu12]. When considering only severe accidents, the relative number of motorcycles and bi- cycles involved in accidents on slippery roads1 is lower than the overall average, see Figure 1.1. In contrast, the percentage of involvement for pedestrians and drivers of mopeds is higher than average under these conditions. A possible explanation may be 1Three road condition categories are used in [Deu12] that can be described as dry, slippery and very slippery (e.g. ice and snow). In this section, slippery refers to a surface with reduced friction due to rain or other impurities on the road, such as leaked oil, leaves or washed-up loam.