Tuesday, October 19, 2010

Effects of Traffic Calming on Montrose Ave: Before and After Study

Traffic calming has previously been shown to reduce instances of speed in the City.  And now here's more poof:

This summer, the City installed a traffic calming island in the intersection of Montrose and 10th Street in order to slow down motorists on Montrose Ave, which has a speed limit of 25mph. This new concrete center-island median is bisected with a ladder-style crosswalk and has added signage to improve visibility.  DPW conducted a "before" study to determine the number of speeders prior to its installation. After letting drivers adjust to the presence of the new island for a couple of months, we conducted an "after" study to compare the island's effect on driver behavior.  Here are the results:
  1. Speeders in excess of 25 mph decreased from 72.5% of all vehicles to 41.3% of all vehicles.
  2. Speeders in excess of 30 mph decreased from 47.7% of all vehicles to 14.1% of all vehicles.
  3. Speeders in excess of 35 mph decreased from 19.4% of all vehicles to  2.4% of all vehicles.
  4. Speeders in excess of 40 mph decreased from 4.7% of all vehicles to 0.3% of all vehicles.
The results, while not perfect, show that speeding drivers slow down dramatically when there is a large concrete island in the middle of the road; speeding drivers apparently prefer slowing down over crashing. Call it blunt, but nothing else reduces speed as much, or is more cost-effective than simply removing, by design, the ability to speed.

Before and After Study showing effect of traffic calming on Vehicle Speeds
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4 comments:

  1. AnonymousOctober 21, 2010 at 2:30 PM

    We wonder what a similar study of the "traffic calming" signs and painted lines on the sides of 4th Street south of Montgomery Street would show?

    ReplyDelete
  2. Bryon WhiteOctober 21, 2010 at 3:52 PM

    Anonymous,
    Here is your answer: In 2005 (prior to the signs and painted islands), speed studies were requested by Councilwoman Robison. These studies showed an average speed of 25 mph on this stretch of 4th Street, with an an 85% speed of about 30mph. In 2009, a speed study at the same location showed an average speed of 24 mph with an 85% speed of about 29mph. Not really an earth-shattering change. Both studies showed that about 1800 cars travel 4th street daily.
    As you know, the City recently removed the "traffic calming" signs and painted islands. These have been replaced with bike lanes.

    -Bryon

    ReplyDelete
  3. AnonymousOctober 27, 2010 at 9:44 AM

    I wonder if yellow cross walk signs (like the ones on Main St) could be placed at the intersection of 5th and Montgomery so that cars would actually realize there are crosswalks there. No cars ever stop when pedestrians are there.

    Also, it would be nice to have a cross walk from Carroll Ave crossing 7th St to get to the library. Walking on the back streets to get to the library (rather than walking on 7th) seems like the best way to avoid a lot of traffic (cars zooming past the side walk), but crossing over 7th to get to the library can be quite difficult and dangerous.

    Thanks.

    ReplyDelete
  4. Bryon WhiteOctober 27, 2010 at 2:29 PM

    Anon,
    We are currently submitting projects into the CIP to address this problem directly, by adding sidewalk to east side of 7th street all the way down to Talbot Ave, in front of the Library. The City Council ultimately approves the CIP, so let them know that you think that this is a priority - there are a lot of residents that share your concern for this stretch.
    Alternatively, when the library gets rebuilt/renovated, I will ask the County to consider improving this stretch of 7th Street when they make their off-site improvements. Not sure which will happen faster at this point.

    I'll look into the pedestrian pedestals for 5th/Montgomery, though this is the time of year that we begin to pull them up for the winter.

    ReplyDelete

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