Rick Harrison at Rick Harrison Site Design Studio has an interesting video on what he calls a traffic diffuser. The video is only a couple of minutes long and its worth the time. Rick rightly points out that traffic engineers don’t do a good job of designing for the mixing of pedestrians with vehicles. Historically, intersections are designed to maximize vehicle throughput while controlling the pedestrians. Washington County in Minnesota put pedestrian tunnels around its multi-lane roundabout in the City of Cottage Grove to remove the pedestrian/vehicle conflict, which is great for vehicular circulation but pedestrians don’t like going into tunnels.
Rick’s concepts will work in neighborhoods where the traffic volumes are relatively low. To move vehicles at busy junctions we’ll still need traffic signals or roundabouts to allow access to/from the minor street. Although his incorporation of the Michigan Left helps from a capacity standpoint.
One minor issue – Rick picks on traffic circles, but doesn’t acknowledge the difference between a traffic circle (usually stop sign controlled with no splitter islands) and a modern roundabout (yield sign controlled, with splitter islands so pedestrians cross half the road at a time, and the roundabout is designed to force all vehicles to go 15 to 20 mph). In my book, there’s no good place for a traffic circle.
Rick is an innovative suburban neighborhood designer (see Rick Harrison Site Design Studio) and his new design software looks intriguing (and inexpensive compared to other CAD systems). I appreciate that as a designer he is thinking holistically about the functionality of the neighborhood. Too often, traffic circulation and access are an after thought in neighborhood design.