Guidelines for the use of no U-turn and no left-turn signs.

The objective of this study was to establish a set of written guidelines identifying traffic and road conditions where No U-Turn and No Left Turn signs should be installed. The effect of these signs on traffic safety was also investigated. A questionnaire was sent to all Virginia Department of Transportation District Traffic Engineers, selected city and county traffic engineers in Virginia, and selected state, city and county traffic engineers outside of Virginia, asking about their current procedures for installing No U-Turn and No Left Turn signs. Eight signalized intersections where these signs had been installed were studied to determine the effect of the signs on left-turn and U-turn related accidents. The signs reduced left-turn and U-turn related accident rates an average of 63 percent for the restricted movement, and 66 percent for the intersection. The decrease in accident numbers paralleled the decrease in accident rates, a 59 percent reduction for the restricted movement and a 62 percent reduction for the intersection. Based on the results from the questionnaire and a literature review, guidelines were established to aid traffic engineers in determining where to install these signs.