Influence of Reaction Time on Calculating Vehicle Speed in Collision, 2nd Edition

摘要

Driver reaction time also known as perception reaction time is a function of perception time, judgment time, initiation time, application execution time and vehicle response time. In other words driver reaction time is a function of driver and vehicle characteristics. The required reaction time for unexpected information is significantly larger than that of expected information. Driver reaction time generally varies from one to two and half seconds. That is a range of 250% from minimum value to maximum value. With respect to driver reaction time many accident reconstruction experts take positions on the extreme ends of range to prove their point. Some experts consider one second is enough while others consider two seconds are needed. To many juries two and half seconds are still not long enough time. In general older drivers slowly process information, make decision and react. Therefore older drivers need more reaction time. In order to accommodate the older drivers AASHTO (2) recommends a criterion of 2.5 seconds for brake reaction time exceeding more than 90th percentile of reaction time for all drivers. Never the driver reaction time should be guessed. There are many computer programs available that incorporate the driver reaction time in preparing the accident reconstruction engineering reports. Never use the computer programs to back calculate the driver reaction time only to win the case. The best way to determine the driver reaction time is to test under real life conditions existed at the time and place of accident. The second best way to determine the driver reaction time is to use relevant published data representing the conditions existed at the time and place of accident. In this book three problems and their solutions representing real life motor traffic were given describing the importance of driver reaction time on collision.