| Autor: |
Levinson, Herbert S., Potts, Ingrid B., Harwood, Douglas W., Gluck, Jerome, Torbic, Darren J. |
| Zdroj: |
Transportation Research Record; January 2005, Vol. 1912 Issue: 1 p72-81, 10p |
| Abstrakt: |
Many state and local transportation agencies install nontraversable medians on multilane highways to improve safety and travel times and to manage local access better. While nontraversable medians restrict direct left-turn access to and from adjacent developments, traffic destined for these locations must use alternate routes, some of which may involve making U-turns at nearby median openings–-a movement often referred to as an indirect left turn. Until recently, the safety effects of increased U-turn volumes have been largely unknown. NCHRP Project 17–21, Safety of U-Turns at Unsignalized Median Openings, documented the safety performance and operational effects of U-turns at median openings. This paper presents the key findings from that research. It presents a summary of key literature and current highway agency practice related to median openings, a detailed classification scheme for median openings, and a summary of the results of comprehensive field studies. The research results indicate that access management strategies that increase U-turn volumes at unsignalized median openings can be used safely and effectively. Analysis of accident data found that accidents related to U-turn and left-turn maneuvers at unsignalized median openings occur infrequently. In urban arterial corridors, unsignalized median openings experienced an average of 0.41 U-turn-plus-left-turn accidents per median opening per year. In rural arterial corridors, unsignalized median openings experienced an average of 0.20 U-turn-plus-left-turn accidents per median opening per year. On the basis of these limited accident frequencies, there is no indication that U-turns at unsignalized median openings are a major safety concern. |
| Databáze: |
Supplemental Index |
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