Traffic planners say reducing four-lane highways on outer Lisbon Street and on Route 4 in Turner is a cheap way to improve safety and cut down on crashes.

Maybe they’re right. By eliminating a travel lane in each direction and adding a dedicated, central turning lane, the flow of traffic would likely slow. Slower cars could lead to fewer accidents and/or ones that are less severe.

The problem is, highway officials can’t point to comprehensive evidence in the state that reducing the number of travel lanes actually improves traffic.

When a proposal to reduce Lisbon Street to three lanes from four near the Lisbon line was proposed in Lewiston, we were skeptical that the change would be beneficial. We saw the move as putting the interest of a convenience store ahead of the concerns of the commuters who use Lisbon Street every day on their way to work in the Twin Cities.

A similar proposal for Route 4 in Turner is now in the works. Route 4 is one of the most dangerous highways in the region. We regularly hear complaints about the high speeds on the road and report on serious – and, too often, deadly – wrecks. Something clearly needs to be done. Once again, we are skeptical that reducing the number of lanes is the best solution.

Last week, we asked state and local officials for the information that they used to determine when it’s appropriate to reduce the number of travel lanes on a road. They offered anecdotal evidence from Brighton Avenue in Portland and a portion of Route 1 in Holden, a change that was made 10 years ago. Needless to say, anyone who’s traveled along Brighton Avenue or through Holden can recognize significant differences between Portland, Holden, Turner and Lewiston. The traffic planners also pointed to a 1999 study from Iowa that looked at roads in Seattle.

A 10-year-old change in Holden, an Iowa study of Seattle and a change on a single road in the state’s largest city make it tough to draw conclusions about the effectiveness of the proposed changes.

Traffic planners agree that a better solution would be to expand the four-lane roads into five lanes, keeping all the travel lanes and adding a fifth lane for turning traffic. But costs, they say, are prohibitive. Reducing the number of lanes is cheaper and allows for more at-grade development.

And that seems to be the key. There are other means of slowing traffic and making roads safer. Increased police patrols and more limited side access could also make the roads safer.

Perhaps going from four lanes to three is the best solution. The evidence, however, falls short.

As the Twin Cities continue to enjoy a renaissance of development, helping traffic flow in and out during peak periods must be considered, even if it limits more sprawling development along Lisbon Street.

We can’t help but think planners are putting the “cheaper” part of the equation ahead of better solutions that account for a growth in traffic volume.