18 Feb Could aerial photography reveal snowless sneckdowns?
While on the way to the studio this morning I came across a great illustration of a sneckdown at Daniel Boone Circle at the end of Eastern Parkway. The circle presents very defined travel routes through the snow making it a very visible example. It also turns out that perhaps this experience has led to a new discovery related to identifying opportunities to further evaluate our street usage.
This sneckdown site I want to call a roundabout, but modern roundabouts typically are not signalized as this one has stop signs at every entry point. Traffic circles, as I understand them are much larger than roundabouts, though they often do have signalized entry. So for the purposes of this example I will just refer to it as a circle.
Without getting into the details of turning radii for emergency vehicles, there are some possible good reasons for the expansive roadway widths around the statue. However, a thoughtful approach to design elements could still improve the experience of the circle for pedestrian as well as drivers, taking clues from the sneckdowns presented. The ambiguity of the current space certainly creates some confusion for drivers, cyclists, and pedestrians entering the circle.
The most interesting observation that came from surveying this location as a sneckdown presented itself back at the studio through Google Maps. There was an “a-ha!” moment as soon as I zoomed into the birdseye view of the circle. Though the aerial imagery is from a warmer season, the same features illuminated by the snow piles were still evident on the roadway. The vehicle tires darkened the street, leaving these negative spaces that were almost identical to the “v” shaped snow piles witnessed today. Could it be possible to utilize high-quality aerial photos to determine other possible sneckdowns without the need for the snow? These, what I call “dodge and burn islands” due to their similarity to the old photography film techniques to accentuate areas of an image, could provide useful visual cues in the same way.
Quickly scanning around at other locations it became clear that there were similar indications of vehicle tire wear, particularly in moderate-to-high traffic intersections that are ambiguous blobs of concrete and asphalt.
This intersection at Baxter and Liberty (above) seemed like a potential test of this idea. The vehicles traveling on Liberty in three lanes of one-way traffic enter the intersection with a 70-foot wide mouth. From the aerial you can see that there is a definite “dodge and burn island” area.
Upon a dashboard survey earlier today, the same feature exists in the snow. This could present a good location to add some type of traffic controlling island and reduce the excessive pedestrian crossing distance.
Utilizing the visual cues of sneckdowns and dodge and burn islands may help inform the strategic location of asphalt reduction. They can illuminate the opportunities for features that improve driver decision-making as well as pedestrian safety. However there are other reasons to remove unnecessary pavement and there is a great example of a dodge and burn island at the intersection of Swan Street, Dandridge Avenue, and Ellison Avenue that the city has since exploited (below).
Here, visible from the historic aerial image from 2010, is a wide intersection that produces a large dodge and burn island in the middle that created a major conflict zone of confusion.
At some point between 2010 and 2012 the street was ripped up and a bioswale water retention basin was put into place (above).
We need to spot check this phenomenon on aerial photos from places around the city to see if these dodge and burn island indicators hold up to the illustrative and well-known sneckdowns, but these could offer another tool to investigate how we use, or don’t use, our streets. If nothing else, it gives us another reason to pour over maps and aerial images.