The city’s Traffic Commission is considering lowering the speed limit from 30 to 25 miles per hour in residential neighborhoods and subdivisions. The cost would be about $200,000 to purchase new signs.
It’s hard to argue against a 25-mph speed limit in residential areas. I don’t have any objection to lowering the speed limit, provided the cost can be spread out by phasing in the changes over a few years. It certainly would be safer, assuming people actually drive slower. The arguments against this effort is that people will ignore the signs (like they do now, it’s argued), thus it won’t be the most effective use of $200,000. They may have a point.
I believe the speeding problem is systemic, and that’s why signs are believed to have little or no effect. To really get people to slow down, some fundamental changes in road design are needed.
When you build a road that has wide, multiple traffic lanes capable of accommodating speeds of 40 or 50 miles per hour, guess what you’re going to get? That’s right: people driving 40 or 50 miles per hour. It doesn’t matter what the sign says; people are going to drive up to the limit that’s comfortable given the road’s design.
Take Knoxville between War Memorial Drive and downtown, for instance: Five lanes (most of the way), 35-mph speed limit. And do you ever see anyone driving 35 miles per hour? Sure you do — you can’t miss them. They’re the ones getting passed by the rest of the motorists who are doing at least 45, if not 50.
This is true in residential areas as well. If you have wide collector streets that can easily handle 40- to 45-mph traffic, that’s what you’re going to see, despite the speed limit signs saying 30 or 25. The roads are wide in the mistaken belief that wide streets equal safer streets. But the inverse is actually true: narrower streets produce naturally lower speeds and end up being safer.
This is the theory behind “road diets.” You can read about it in this PDF report by Dan Burden and Peter Lagerwey. They write:
Nationwide, engineers are putting roads on “diets,” helping them lose lanes and width. In the process formerly “fat” streets often become leaner, safer, and more efficient. They become multi-modal and more productive. In many cases these former “warrior” roadways are tamed and turned into “angels.”
Often these changed roads set the stage for millions or megamillions of dollars in new commercial and residential development. The change can increase value of existing properties. In some cases costs of reconstructing roadways are repaid in as little as one year through increased sales tax or property tax
revenue.
The “Road Diets” report focuses on reducing arterial roadways. However, narrower streets (in concert with other calming measures, such as on-street parking) have been shown to reduce speeds and make roadways safer in general, as this report from the Institute of Transportation Engineers (ITE) shows.
To effect change in this area, the city’s subdivision ordinance would need to be amended, since that is where the design standards for street widths and on-street parking are codified (Municipal Code, Appendix A, Article V, Part I). Until changes are made to the way we build our roads, speeding is going to continue to be a problem, no matter how many signs we put up.