Unsafe crosswalks

Crossing the street is risky. The longer the crossing distance, the greater the risk.

The greater the distance, the greater the risk

Mass. Highway, the state agency that will be ruling on whether the Town’s rebuild plan can go forward, has this to say about crossing the street:

Marked or unmarked, pedestrian crossings should be as short as possible. At all intersections, reducing the time pedestrians are in the crosswalk improves pedestrian safety and motor vehicle and bicycle movement. (Source: Highway Design Guide, p. 6-61)

Mass. Ave.’s crossings are all 66 feet or longer. How does that stack up?

According to Mass. Highway,

In general, fifty feet is the longest uninterrupted crossing a pedestrian should encounter at a crosswalk. (Design guide, p. 6-63)

50 feet is the safety limit

Why fifty feet? It sounds a little arbitrary, and as you can see there is some wiggle room with that “in general.”

But the people in my neighborhood  are not interested in skirting the guidelines. We care about safety. Mass. Highway is saying that risks at fifty feet are about as bad as ought to be built in to a street.

More distance in a crosswalk means more time in which one could be struck by a car. Also, longer crosswalks mean multiple lanes, which pose their own unique multi-lane danger to pedestrians.

Through sidewalk bump-outs and pedestrian refuge islands, the Town’s plan for the street would shorten every crosswalk, most (though not all) to less than 50 feet. A whole lane would be eliminated, making an entire category of pedestrian crashes impossible on the outbound side of the street.

Shorter crossings also speed vehicular traffic, as cars and bikes don’t have to wait as long for the peds to get across. (You do stop for pedestrians, don’t you?)

Note for data geeks: My “very simple” charts are, obviously, very simple, meant to suggest the general relationship between crossing distance and safety. In reality, the trend line does not begin at zero feet (think about it) and is probably bumpy to reflect the effect of adding lanes and their related multi-lane threats.

But it does trend up.

Update: The Arlington Advocate for this week (February 24) has a solid story about this issue.

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5 comments so far

  1. Mark Kaepplein on

    The design guideline of 50′ works out to be two inner 11′ lanes and two outer 14′ curb lanes. Parked cars plus their door zones protect pedestrians at each end (alternately, bump outs), so 70′ road width still keeps exposure to 50′. Put a raised pedestrian median to halve the continuous exposure, and road width can go to eight traffic lanes plus two parking lanes within guidelines! Less than 50′ exposure is better, so we should add raised refuge islands where supported by room and crossing volumes, such as around Lake Street. Moving the T stops just over a block east will further reduce conflicts and risk, while improving traffic flow of turns with Lake.

    Studies and data that I’ve found only support three road features showing measureable pedestrian safety benefit: narrower roads, raised refuge medians, and raised crosswalks. Raised crosswalks are completely inappropriate on an artery with volumes of Mass. Ave. and not so popular with cyclists either. Additionally, ramps, bumps, and humps take their toll on expensive fire engines and laddar trucks, shortening their lifespan. While not a road feature, lighting improves safety in the most dangerous times of the day – dawn, dusk, night.

    Just because something is in the design manual does not make it true. Curb extensions, neck downs, and reduced radius turns are advocated, yet no data seems to exist showing any efficacy. Worse, no negative aspects of the features are listed at all, only positives! The bike design guide even starts with a false claim in the very first sentance; that bikes have been in use for hundreds of years, when it is less than 200. Bikes then really only got popular after roads were paved for cars.

    We should give credit to the town for violating design guidelines in our current painted crosswalks! They have wider painted lines and overall width than specified in the design guide. This, however is smart design – they are more proportional to the visual width of the roadway. The previous skinny, narrow crosswalks were not nearly as obvious to drivers, thus more dangerous, and we may even have enough data to show that.

    The interesting data challenge is making an accurate risk vs. crossing distance chart, seeing the curve of the graph and a knee around 50 feet. Getting complete data on accidents is very hard, so difininitive results are rare. Seldom does a researcher know the road configuration, drug and alcohol content of the pedestrian and driver/biker, ages, mobility, lighting, weather, speeds, clothing color visibility, vehicle visibility, j-walking or not, travel directions and impact angle, visibility distances etc.. Drunk pedestrians J-walking at night in dark clothing are most likely to get hit by a pickup truck, SUV, or car (in that order, normalized). That’s more natural selection than road design.

    • Adam Auster on

      The design guide is relevant not because it is infallible but because it is the standard that we must meet.

      There is some built-in flexibility to that standard but this is one requirement we should not seek to circumvent.

      On that score I do not think Mass. Highway would like your 14-foot shared-lane idea, unless you take out the adjacent parking.

      The agency prefers 15- or 16-foot shared lanes when next to parking (or alternatively bike lanes). This is another sensible requirement that we should not want to overthrow.

      Your comments about drunken jaywalkers and natural selection seem disrespectful of the actual victims of car-pedestrian crashes on Mass. Ave.

      • Mark Kaepplein on

        Yes, break guidelines, and MassDOT makes comments. They did this for specifying 6″ thick concrete on sidewalks instead of standard, cheaper, 4″ thick, also for wider, more visibe, more expensive, crosswalk paint stripes than standard.

        The drunken j-walker comment was to highlight the worst-case sum of causes for most pedestrian accidents. I don’t claim those are Arlington’s pedestrians, just that the hypothectical pedestrian would almost have to consciously multiply their risk factors that way and choose who hits them.

        Most pedestrian accidents are completely out of the influence of road designers, and all but one are controlled by the pedestrian. This is where the video link and risk taking by people relate. Night can’t even be turned into day due to light pollution regulations. The one risk factor that can be helped by road designers is J-walking, however, the fire chief reportedly doesn’t want lots of raised refuge median that Cambridge used, and has veto power. There also isn’t room for it in some places in order to maintain 4 lanes and not do more utility pole moves.

  2. Mark Kaepplein on

    Entertaining video on fear, profit, actual risks and effective solutions, and why not to wear a bike helmet:
    http://video.tedxcopenhagen.dk/video/911034/mikael-colville-andersen
    Bike helmets discourage cycling generally and promote more risk taking by cyclists wearing them.

    • Adam Auster on

      Mark, what does this have to do with anything?

      I welcome your attention and your thoughts, but I ask you to confine your comments to something like the topic of the post. It’s a courtesy to anyone else reading here.


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