Road diet

A road diet, also called a lane reduction or road rechannelization, is a technique in transportation planning whereby the number of travel lanes and/or effective width of the road is reduced in order to achieve systemic improvements.

A typical road diet technique is to reduce the number of lanes on a roadway cross-section. One of the most common applications of a road diet is to improve safety or provide space for other modes of travel. For example, a two-way, four lane road might be reduced to one travel lane in each direction. The freed-up space is then used to provide or enhance some of the following features:

If properly designed, traffic does not divert to other streets after a road diet, because the road previously provided excessive capacity. In other scenarios, reduction of traffic (either local traffic or overall traffic) is intended in the scheme. Road diets are usually successful on roads carrying fewer than 19,000 vehicles per day. Road diets can succeed at volumes up to about 23,000 vehicles per day. However, more extensive reconstruction is needed. Examples include replacing signals with roundabouts, traffic calming on parallel streets to discourage traffic from diverting away from the main road, and other means to keep traffic moving smoothly and uniformly.

In a lane diet, the width of a lane is decreased to reduce vehicle speeds and yield space for other use. Typically vehicular travel lane widths are narrowed to no more than ten feet, and left turn (in countries where drivers use the right-hand side of the road) storage lanes to nine or ten feet. Resulting space can be applied to pedestrian refuges, medians, sidewalks, shoulders, parking, or bike lanes. Lane width guidelines in the United States are offered as a range and lane diets fall within this range.

In many cases of 4-lane roadways with double-yellow, this can present a hazard for oncoming traffic in the "passing lane", as well as left-turners. Sometimes 4-lane with double-yellow is upgraded to 5-lane with center turn lane since that practice is more of an upgrade than a "diet" like 3-lane with center turn lane is.

Proponents of road diets generally believe key benefits include lower vehicular speeds, reduced crash rates, and improved pedestrian safety. Other benefits of road diets include promoting better land use, reducing induced traffic, promoting greater driving attentiveness, and promoting cycling through the addition of bicycle lanes. Providing dedicated left turn (in countries that drive on the right-hand side of the road) lanes at intersections can improve vehicular safety and can enable efficiency gains along the roadway.

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Wikipedia