Ramp Metering

Across the Country

Ramp meters are not only being used in the Kansas City area, but also in metropolitan communities across the country including Milwaukee, Portland, Seattle-Tacoma, Phoenix, Minneapolis-St. Paul, Denver and more. Such communities have been using them for some time and are benefiting from ramp metering programs in a number of ways.

Improved Safety

Congestion happens when groups of cars enter the freeway and compete for openings in the mainline flow of traffic. Merging is more difficult and more challenging for drivers if ramps are close together or if acceleration and deceleration lanes are short. Sideswipe and rear-end accidents can be the result. Ramp metering improves safety by decreasing accidents. According to the Federal Highway Administration:

• Accidents on I-435 in Kansas City dropped 64% after the ramp meters were installed.
• Seattle's ramp meters decreased the overall accident rate by 39%
• Portland's reduced the peak period accidents 43%
• More consistent traffic flows
• Minneapolis' lowered peak period accidents 24%
• Denver's ramp meters cut rear-end and side-swipe accidents 50%

Enhanced Mobility

Even if freeways are not congested, seven or eight vehicles merging onto the freeway at the same time can be an issue for motorists. Ramp meters decrease the number of sudden weaving and breaking movements. By regulating the flow of the cars, ramp meters allow more vehicles to use the freeway, improve freeway speeds, and lower travel times. Information from the Federal Highway Administration indicates:

• Travel times along south I-435 improved when ramp metering was added
• Denver's ramp meters have increased rush hour travel speeds 57% and decreased travel times 37%
• Seattle's ramp meters have lowered average travel times 52%
• Ramp meters in Minneapolis increased rush hour volumes 25%

A Better Environment

Roadways can move traffic and benefit the environment at the same time. When they promote smoother traffic flow and allow drivers to drive at or near the posted speed limit, roadways reduce the amount of vehicle pollutants that are released into the air and make less of a contribution to existing ozone levels. Ramp meters help lower vehicle emissions and fuel consumption by decreasing the time that cars spend waiting in traffic. Any time spent waiting on freeway on-ramps is made up in travel time saving once on the freeway.