Although studies have shown that human error is one of the main causes of traffic accidents, too often this fact is used to justify inaction on behalf of road authorities and vehicle manufacturers and it also leads to lack of public support for such measures. While it may be true that in 70% to 90% of all accidents, human error is recorded as a contributing factor on accident reports, road and vehicle improvements can greatly reduce the likelihood of human error or the consequences of the accident. For example, driver errors initiate most "single vehicle-lost control" accidents; however, the location of rigid roadside structures such as sign posts, utility poles, and culverts is a critical factor in determining the likelihood that off-roadway accidents result in collisions. Engineering solutions related to both the vehicle and the road offer greater safety opportunities than simple accident statistics might indicate. The transportation engineering principles and practices described throughout this handbook, when applied correctly, will contribute to the reduction of accidents through the design, construction, and operation of safer streets and highways.
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