Page - 2 - in Maximum Tire-Road Friction Coefficient Estimation

1 Introduction that many pedestrians and moped drivers cannot postpone the planned journey because of the weather and are also limited in selecting alternative means of transport. 27 % of all accidents involving personal injuries and passenger cars occurred on slippery roads. Ice and/or snow was responsible in 4.8 % of all cases. When considering all slightly injured traffic participants, these numbers are slightly lower. An analysis of the traf- fic accidents in terms of the lighting conditions shows similar tendencies. There is no significant relationship between snowy/icy road condition and injury severity except for severe accidents involving material damage, see Figure 1.2. The percentage of people killed is slightly higher on slippery roads. 0 5 10 15 20 25 30 a) Severely injured persons A ve ra ge M op ed s M ot or cy cl es Pa ss en ge r c ar s B ic yc le Pe de st ria n 0 5 10 15 20 25 30 b) Slightly injured persons M op ed s M ot or cy cl es Pa ss en ge r c ar s B ic yc le s Pe de st ria n A ve ra geP Rain, Oil, Leaves,... Snow, Ice Figure 1.1.: Influence of road condition on accidents in relative numbers by selected categoriesof roadusers fora) severely injuredpeople, andb) slightly injured people, based on Destatis, [Deu12]. Two of three road condition categories are shown; the remainder of the accidents occurred on dry roads. The high number of passenger car accidents caused by bad road conditions is partly due to inadequate driver adaptation of the longitudinal speed under such road condi- tions. Studies show that drivers adapt the speed, but not enough to avoid collisions or unstable vehicle conditions when braking or cornering, e.g. [SS90], [Saa93] and [Roi93] as cited in [WWO97]. The drivers must use optical, acoustic and haptic cues to esti- mate the friction potential during driving since no direct measure is available. Heinijoki showed that non-expert drivers have difficulties gauging the current road conditions, especially for low friction potentials, [Hei94] as cited in [WA01]. These investigations highlight the importance of assisting the driver. A robust and reliable estimate of the friction potential is assumed to be one effective countermeasure 2