The East Coast’s first protected intersection is coming to Silver Spring. Here’s how it works.
Image by Montgomery County Division of Transportation Engineering.
Montgomery County is installing a protected intersection in downtown Silver Spring, the first of its kind on the east coast. It’s an important step toward building streets that are safer for vulnerable road users, like people walking and bicycling.
The intersection, currently under construction, is located at Spring Street and Second Avenue. The Montgomery County Division of Transportation Engineering Twitter account wrote a lengthy explanation of how it works, complete with some great gifs:
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— MC_DTE (@MoCo_DTE) August 1, 2019
You may have heard that Montgomery County is getting the first “protected intersection” on the east coast. But what is it? And how does it work?
We’re glad you asked!
The intersection is under construction, and is at Spring St and Second Ave in downtown Silver Spring. pic.twitter.com/22UHiwVJct
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— MC_DTE (@MoCo_DTE) August 1, 2019
This intersection will be where two separated bike facilities converge.
On Spring Street, one-way separated bike lanes run east to Wayne Avenue, completed in 2017.
On Second Ave & Wayne Ave, a cycletrack is under construction south to Georgia Ave. pic.twitter.com/AU2c4c31EE
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— MC_DTE (@MoCo_DTE) August 1, 2019
The protected intersection is specifically designed to maximize safety for cyclists & pedestrians. It has several elements that work together to meet that goal.
The first major element is the corner island. pic.twitter.com/sp7txL8b4h
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— MC_DTE (@MoCo_DTE) August 1, 2019
The second major element is the advanced stop line for bikes. pic.twitter.com/bI21cmX6A8
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— MC_DTE (@MoCo_DTE) August 1, 2019
The third major element are the set-back crossings.
Now, let’s go over how the three elements work together. pic.twitter.com/QClSUYTsYf
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— MC_DTE (@MoCo_DTE) August 1, 2019
The corner islands’s primary goal is to slow down drivers turning right. The tightened radius means that drivers turn very slowly. A raised apron allows larger vehicles to turn by mounting it if necessary.
Speed is the critical factor in crash survivability. pic.twitter.com/Srqc0eiM0f
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— MC_DTE (@MoCo_DTE) August 1, 2019
The corner island also introduces a lateral shift for cyclists. This slows down cyclists traveling through the intersection.
The combination of drivers turning right slowly and cyclists entering the intersection more slowly increases reaction time and reduces crash severity. pic.twitter.com/aySnE3uOab
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— MC_DTE (@MoCo_DTE) August 1, 2019
That means that both drivers and cyclists have more time to react to avoid a crash. But if there is a crash, it is much less likely to be severe, and more likely to be survivable.
The corner islands also give turning drivers a place to wait out of the flow of thru traffic.
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— MC_DTE (@MoCo_DTE) August 1, 2019
The advanced stop line and lateral shift give drivers waiting to turn right better visibility of cyclists waiting at the intersection and approaching it.
Instead of looking over their shoulder or in their wing mirror, drivers can see cyclists through their passenger window. pic.twitter.com/eA7SFw0QS4
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— MC_DTE (@MoCo_DTE) August 1, 2019
The corner islands, set-back crossings, and advanced stop line give cyclists a head start in their crossing. Cyclists proceed on the same green as drivers, but they’re closer to the intersection.
The head start also improves visibility. pic.twitter.com/49tXOflUcy
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— MC_DTE (@MoCo_DTE) August 1, 2019
The corner islands also reduce the exposure of both pedestrians and bicyclists crossing the intersection.
Without the islands, pedestrians face exposure to vehicles from curb-to-curb. With the islands, the crossing exposure is reduced by about 12’ on each side. pic.twitter.com/eHuaZF69kM
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— MC_DTE (@MoCo_DTE) August 1, 2019
The corner islands also provide queuing space for cyclists turning left. This space allows through cyclists to pass behind the cyclists waiting at the advanced stop line for the green signal. pic.twitter.com/RJG3yyad8e
The agency says that the next step for the project is milling and paving, which will start around August 11. Readers: Have you used an intersection like this before? What are your thoughts?