Road Diets

Why Put a Road on a Diet?

During the past several decades, there have been many roadways constructed in urban areas that have four lanes. When a road is widened, it often comes with a trade-off: more and wider lanes, with less sidewalks and paved shoulders. In many cases, these roadway improvements allow more cars into traffic streams, encouraging communities to become more car dependent. These changes often generate higher vehicle speeds, noise, and danger to people trying to walk, bike, shop, or live on or near main streets.

Use of public transportation is sometimes discouraged when pedestrians have difficulty crossing four lanes of traffic to get to a transit stop. Minimal areas of sidewalk and vegetation also detract from a community's visual appeal and can impact the health of neighborhoods and businesses on many levels.

When drivers use four-lane roadways, they assume that there are always spare lanes in their direction. They tend to drive faster than they should. Motorists using multilane roads seek to match speeds of other drivers, and speeding drivers tend to set prevailing speeds. As traffic volumes increase, especially at rush hour, risk of high-speed driving increases.

During peak volumes of traffic, right- or left-turning movements occur. When a car stops in a moving traffic lane to turn left, it causes congestion, blind spots, unsafe lane changes, and changes in vehicle speeds. Quick lane-changing maneuvers can lead to serious rear-end crashes. Drivers may also move from lanes of slowing traffic directly into the backs of other vehicles that have slowed for their turns. These are only a few examples of traffic and driving behaviors on four-lane roads that have been known to cause accidents.

Benefits

When roadways have been modified from four travel lanes to two travel lanes with a two-way left-turn lane, research has shown a 29 percent reduction in all roadway crashes. Road diets provide a center turn lane so that left turns are simpler. A driver crosses only one lane of traffic at a time, resulting in fewer blind spots. With an undivided four-lane road, a driver must find a gap in two or three lanes of traffic at once to make a left turn. With only three lanes of traffic, there are also fewer intersection conflicts.

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