by Michael Brown, PE, AICP
* Traffic Engineer, New Urbanist, Founder of Urban Innovators
How to Eliminate a Traffic Lane
A typical suburban arterial might carry about 700 vehicles per hour per lane. But if revamped to include innovative intersections, the boost might jump to 1,100 vehicles or more.
How can more cars per lane help alternative modes?
The increased capacity doesn’t need to be for cars! In this chart, suppose you currently have an arterial with 3-lanes each direction. Each lane carries 700 vehicles per hour per lane (blue), or 2,100 total.
With Innovative Intersections, just two lanes can carry 2,200 - about the same as today with 3-lanes. Now you can easily give the third lane to transit, or cycle tracks, without impacting traffic!
Narrowing Lanes
If you can’t quite give up a lane, you might be able to get “parts of lanes.” Engineers usually want 12-ft lanes for anything signed at 40-mph and higher. But when efficient intersections reduce delay, then you can reduce speeds to 35 or less without hindering average speeds. 35 mph and below is where a new 10-ft standard kicks in. That’s the best-practice width for walkable boulevards supported by the Institute of Transportation Engineers, Congress for New Urbanism, and National Association of City Transportation Officials (ITE, CNU, and NACTO).
Try out StreetPlan.net, a free Complete Street cross-section design tool that uses “red / yellow / green” to guide you through context-based best-practices for speeds, lane widths, and other street attributes.