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Thursday, December 16, 2010

Let's Be Creative and Save Lives

After a long discussion in committee centered around lowering the speed limit in a mid city pedestrian zone it became apparent that city planners and traffic engineers have a basic concern for non-impeded traffic flow. This is not news to those who look to better ways to provide for safe pedestrian crossings, designated bike lanes, and a sense that a city is, in fact, walkable or bikeable. The resistance to slowing traffic was spelled out in the sentence,"The road was built to move traffic around the city efficiently." At this particular zone it is not uncommon for autos and trucks to reach speeds of 50 miles per hour in a 40 mile per hour zone. Lowering the limit to 30 miles per hour was seen as the best scenario for safety but the engineer involved stated that because of the way the road was designed traffic would move at a much higher rate of speed. One solution the group arrived at was to put the street on a Road Diet by reducing lanes in the zone from four 12 ft. with no medium to two lanes with a center island and turning areas. It has been shown that by adding elements along and in the roadway that physically show a driver that there is an awareness that this zone is a much different travel space than the rest of the long boulevard. With this comes a rise in caution and greater awareness of speed. By changing the texture of an intersection with stone pavers, using audible strips before entering the zone, and providing well signalized crosswalks a driver is much more alert to the presence of foot and bicycle traffic. Fortunately this roadway is scheduled for major sewer and water line work in the coming year and we now have an opportunity to redesign the streetscape with a better end result in mind. Increased driver awareness can take many forms as discussed above but education for drivers is essential in local campaigns and in short PSA's such as this one. After all, speed does kill.

1 comment:

  1. Excellent point about the fact that excessive speed does kill. The engineer is right in that simply reducing the speed limit does not tend to change driver behavior; but road redesigns do. Depending on the nature of the traffic on the road, a road diet may or may not work. Generally, 4 to 3 road diets work on roads up to 20,000 vehicles per day, and work especially well when there is much turning as opposed to through traffic. If the traffic is spread out over the day, then the 20,000 figure goes up. OTOH, if the traffic is overwhelmingly through traffic, then a 4 to 3 road diet may create problems.

    Interestingly, I remember reading about how the overall throughput of a road in terms of net traffic moved follows some sort of inverted U curve with regard to speed. Go too fast, and capacity drops because cars need to be spaced out too much. Minimizing delays at intersections can easily compensate for lower overall speeds on surface streets, which is why roundabouts so dramatically improve traffic flow at busy intersections.

    The video reference is an excellent one. I'll quote it for everyone's reference.

    When a pedestrian is hit at forty mph, there's a 70 % chance they'll die. At thirty mph, there's an 80% chance they'll live
    New York City Department of Transportation