Traffic speed and safety on local roads at residential area

The rapid door-to-door journey times made possible by motor and road system are one of the great benefits offered by modern transport. The level of speed that makes this journey-times possible have also effects in terms of operation costs, noise, exhaust emissions and the occurrences of traffic accidents and consequent death, injury and material damage. Speed limits are one of the major factors that affect the drivers and other road users (pedestrians and bikers) in terms of traffic safety, transport efficiency and comfort. The speed should be presented reasonably according to the road characteristic, road condition and road safety. A lower and higher speed limit does not only harm the driver but also causes a higher number of accidents. According to the real situation in Yogyakarta, most drivers hardly obey the posted speed limit due to unrealistic speed limits. They usually drive faster than posted speed limit because road condition can support drivers to run in higher speed. This research is aimed to understand traffic characteristics on the local road, identify the problems arising due to speed restriction, and determine the method to reduce the traffic speed in local road. The objects of study are Jambon and Pandega Marta roads, which are local road at residential area with high vehicles speed. Preliminary survey consisting of visual observation and traffic volume was carried out to determine the survey location. Speed measurement and drivers speed behaviour are applied to collect the needed data. The collected data are compiled and analysis using MS Excel. Z-test was used for inferential statistic. The 85th percentile of speed is used to determine the free speed. From data analysis and discussion it can be concluded that both Jambon road and Pandega Martha road have the same traffic characteristisc and speed as well. The mean speed is around 37 – 39 km/h and the 85th percentile speed is around 45 – 48 km/h. The mean speeds in both roads are exceeded the speed limit for residential road that is 30 km/h. To reduce speed to be around 30 km/h, 200x 10 x 72cm speed hump with spacing between speeds humps of 251m on Pandega marta road and 200x 10 x 77cm speed hump with spacing between speeds humps of 234m on Jambon road can be used. To be effective for speed reducing, the installation of speed hump can be combined with instillation speed limit sign, raised crosswalk, and raised intersection.