Tools For Sustainable Transportation

Lane Conversions: equitable and efficient streets for all

A lane conversion is a simple and powerful tool for making our shared transportation system better for all. There are many names for this technique, including 'road diet', 'right sizing' and '4 lane to 3 lane conversion'. This last term, '4 to 3 lane conversion', is often the most appropriate and accurate, as that is what communities throughout the United States have been doing for a couple decades now, and continue to do today.

Missoula has had essentially three of these types of conversions. All three conversions have significantly lowered crashes while generally improving traffic flow for all modes. The addition of a center turn lane in the lane conversion projects has improved motor vehicle flow and increased walking and cycling rates.

Here is a diagram of a 4 to 3 lane conversion:

4 to 3 lane conversion example

The 3-lane street matches well with another sustainable transportation tools- the modern, single lane roundabout. The center turn lane on a 3-lane street can seamlessly transition to become the splitter island of the roundabout. Solving congestion and safety for all can often be achieved by converting undivided 4-lane urban streets to 3-lane streets and utilizing single lane roundabouts instead of traffic signals.

Changing from 4 lanes to 3 (or 5 lanes to 3, or 5 lanes to 2- there are many ways to convert lanes) gives more space to improve walking and cycling facilities, as well as inserting green space. Making space for walking and cycling releases the latent demand for these modes of active transportation and usage starts to climb. Making a city greener, with landscaping, gardens, trees and habitat ends up lowering stress levels and increasing livability.

Lane conversions increase safety and access along and across arterial streets for people walking, biking, driving and using public transit. Enticing and encouraging people to walk, bike and bus more often by enhancing facilities is a good way to improve community stability and sustainability.