Greater Greater Washington

Posts in category Smart Growth

Wider lanes make city streets more dangerous

The "forgiving highway" approach to traffic engineering holds that wider is safer when it comes to street design. After decades of adherence to these standards, American cities are now criss-crossed by streets with 12-foot wide lanes. As Walkable City author Jeff Speck argued in CityLab last year, this is actually terrible for public safety and the pedestrian environment.


The rate of side impact crashes is lowest on urban streets with lanes about 10.5 feet wide—much narrower than the standard 12 feet. Graph by Dewan Karim via Streetsblog.

A new study reinforces the argument that cities need to reconsider lane widths and redesign streets accordingly. In a paper to be presented at the Canadian Institute of Traffic Engineers annual conference, author Dewan Masud Karim presents hard evidence that wider lanes increase risk on city streets.

Karim conducted a wide-ranging review of existing research as well as an examination of crash databases in two cities, taking into consideration 190 randomly selected intersections in Tokyo and 70 in Toronto.

Looking at the crash databases, Karim found that collision rates escalate as lane widths exceed about 10.5 feet.

Roads with the widest lanes—12 feet or wider—were associated with greater crash rates and higher impact speeds. Karim also found that crash rates rise as lanes become narrower than about 10 feet, though this does not take impact speeds and crash severity into account. He concluded that there is a sweet spot for lane widths on city streets, between about 10 and 10.5 feet.

In Toronto, where traffic lanes are typically wider than in Tokyo, the average crash impact speed is also 34 percent higher, Karim found, suggesting that wider lanes not only result in more crashes but in more severe crashes.

The "inevitable statistical outcome" of the "wider-is-safer approach is loss of precious life, particularly by vulnerable citizens," Karim concluded.

Coast Guard employees are using the Anacostia Metro station in a weird way

Metro recently released data showing where Metrorail riders go from each station, and as one of our commenters noted, the most-frequented destination for people traveling from Anacostia is... Anacostia. That's because Coast Guard employees and contractors use the Anacostia Metro as a pedestrian tunnel.


Entrance and exit through the same station by volume in October 2014. Image by the author.

As commenter Andy pointed out, when a passenger enters at Anacostia during midday, afternoon peak, and evenings on weekdays, they're most likely to exit from the same station. Not only that, but as the chart above shows, entering and exiting at the same station is more common at Anacostia than at any other station in the system. Why?

At St. Elizabeths, where the Coast Guard's headquarters moved in 2013, the National Capital Planning Commission's parking policy allows one parking space for every four employees. That means the Coast Guard is limited to only 931 parking spaces for its 4000 federal employees and numerous additional contractor employees.

Unlike at NIH, the St. Elizabeths campus is over a mile walk from the closest Metro, there are no nearby parking lots, and street parking is limited.

The A4 bus, which leaves from the Anacostia Metro bus bay, runs directly to the campus. So many people who work at St. Elizabeths park in the 800-space garage at the Anacostia Metro, tap into the system at the garage entrance so they can walk through the station, and tap out at the exit closer to the bus bay. From there, they take the A4 to work.


The walking path from the Metro garage to the bus bay. Image from Google Maps.

It's not hard to understand why commuters might opt to use the Metro station as a pedestrian walkway. While the walk down Howard Road from the parking garage to the bus bay is less than a quarter of a mile, it requires commuters to walk an empty stretch of road, under I-295 and across a highway on and off ramp.


The walking path from the Metro garage to the bus bay. Image from Google Maps.

The accidental pedestrian tunnel won't be around for much longer. In the 2014 Coast Guard Transportation Act, Congress overrode the NCPC. Between now and 2017, the Coast Guard will be required to allocate an additional 1,000 parking spaces at St. Elizabeths.

The guy who invented the mall hated cars

Many great minds have opined on cities, design, and urban planning. But few have made such a stark and apocryphal statement as this:


Photo by Chapendra on Flickr.
One technological event has swamped us. That is the advent of the rubber-wheeled vehicle. The private car, the truck, the trailer as means of mass transportation. And their threat to human life and health is just as great as that of the exposed sewer.
Strong words, indeed. But what is more surprising is who uttered them: none other than Victor Gruen, the man who invented the enclosed shopping mall that so came to be nearly synonymous with the American suburb.

A recent episode of the 99% Invisible podcast discussed Gruen's career as an architect and noted the seeming dissonance between his work (the shopping mall) and how much he hated cars.

Like many architects and planners of the post-war era, Gruen was attempting to deal with a society facing radical changes in the built form: cities were starting to be hollowed out by parking lots and urban renewal, and the automobile-centric suburbs were starting to sprawl across the landscape. He saw the American suburbs as lacking in the types of "third places" necessary for social engagement. He thought the fact that everyone drove everywhere severely limited social engagement and interaction.

His solution was to build a large enclosed public space centered on a climate controlled court. It would include retail arranged in a sort of main street style with small storefronts facing pedestrian walks. But cars, of course, would be banned. This is the form the typical shopping mall took.

Gruen's vision didn't stop there, though. He actually intended for the mall to be the centerpiece of a mixed-use neighborhood. The projects would include offices, apartments, public services, and other amenities. And within this space, the pedestrian would be king.

That's not how things turned out. The first of his projects, the Southdale Mall in Edina, Minnesota, near Minneapolis, was built with only its retail components. And it was surrounded by a sea of parking. People might walk within the mall, but they almost certainly drove to it.

For a fuller discussion of Gruen's vision and his disappointment with how it turned out, make sure to listen to this episode of 99% invisible. The design-focused podcast offers an excellent overview of the built environment and the other ways that design (invisibly) influences our lives.

Fairfax is getting 22 new bike lanes in 2015

When Fairfax County repaves roads this summer as part of routine maintenance, it's going to add bike lanes and other features to some of them.

Here's the complete list of Fairfax streets that will get new bike facilities in 2015:


Image from VDOT.

Among all the roads due for repaving this summer, 22 will get bike lanes or sharrows. Some of the additions are coming as part of road diets.

Adding bike infrastructure to roads that are going to get a new coat of paint either way is a very cheap way to make Fairfax more bike-friendly. Of course, if this were the only way the county added new bike lanes, it'd take quite a while for them to show up on recently repaved roads.

The projects are spread throughout the county, but Tysons is getting some special attention as the county takes another step in its planned transformation of the area.

VDOT's website says residents will begin seeing the new paint—and lanes—in June.

Modern streetcar planning in the region, visualized

This week we looked at streetcar planning in Anacostia, H Street and Benning Road, and Northern Virginia. To help visualize this evolution, here's an illustration of how and when all of these plans have changed over the last 20 years.

Slideshow image


March, 1997: A Transportation Vision, Strategy, and Action Plan for the Nation's Capital
Proposed three streetcar routes (and one crosstown Metro line).


April, 1999: WMATA Transit Service Expansion Plan
Identified three possible streetcar lines among a multitude of future transit projects.


August, 1999: Crystal City / Potomac Yard Area Transportation Study
Proposed a streetcar for the transit corridor.


January, 2002: DC Transit Development Study (WMATA)
Identified four possible streetcar corridors and initiated the study of a starter line in Anacostia.


February, 2003: Columbia Pike Transit Initiative
Proposed streetcar service as an alternative for the corridor.


March, 2003: Crystal City / Potomac Yard Transit Corridor Alternatives Analysis
Selected Bus Rapid Transit (BRT) over streetcar for the corridor.


October, 2005: District of Columbia Transit Improvements Alternatives Analysis
Proposed four streetcar lines. Construction started on Anacostia Demonstration Project.


June, 2008: District of Columbia Transit Improvements Alternatives Analysis (2008 Update)
Modified proposed streetcar network. Construction of H Street/Benning Road line begins and the Anacostia line gets realigned.


October, 2009: District of Columbia Transit Improvements Alternatives Analysis (2010 Update)
Proposed a 37-mile, 8-line streetcar network.


July, 2011: Route 1 Corridor Streetcar Conversion Project
Study of converting transit corridor to streetcar initiated.


June, 2012: 22-Mile Priority Streetcar System
Focus of DC Streetcar efforts scaled down to three lines; Anacostia line truncated.


October, 2014: 8.2-Mile Streetcar System
Focus of DC Streetcar efforts scaled down to two lines amid funding cuts.


November, 2014: Arlington Cancels Streetcar Projects
Both Columbia Pike and Crystal City / Potomac Yard streetcar efforts indefinitely suspended.


March, 2015: New Administration Commits to One Line
Mayor Bowser commits to completing the H Street/Benning Road streetcar line. Future lines remain uncertain.

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