Brookline bicycle crashes: patterns and factors

Chief Daniel O’Leary of the Brookline Police Department wrote an analysis of bicycle crashes, based on his department’s records for 2013. It shows the highest density of crashes for that year on Harvard St. between Auburn and Verndale Sts. He also provided to the Bicycle Advisory Committee some detailed information about the 53 bicycle crashes police investigated in 2013: on average, about one a week. Several patterns appear.

Patterns: Three-quarters of bicycle crashes occurred from May through October: 40 during the six warmer months, compared with 13 during the six colder months. Few crashes occurred from 8 pm to 8 am–6 reports–compared with 8 am to 8 pm–47 reports. Most crashes occurred during daylight hours in warmer months. A bicycle crash around 10 am in summer was about 20 times as likely as a bicycle crash around 10 pm in winter.

All the police reports from Brookline were for collisions involving motor vehicles, bicycles and pedestrians. Peak hours for bicycle crashes were late morning, 10 am to noon, and late afternoon, 4 pm to 6 pm. None of the police reports from Brookline were for bicycles falling over or colliding with fixed objects. However, a long-time Boston-area bicyclist and observer reports that “most injury-producing bicycle crashes do not involve a motor vehicle at all.”

Circumstances of bicycle crashes are harder to understand. For about two-thirds of Brookline bicycle crashes, bicyclists were transported for medical attention. No fatalities were reported for 2013, but the extents of injuries were not otherwise described. Police reports of primary causes did not appear to follow a uniform system and needed to be categorized. Grouping them into five categories yielded the following:

Motorist struck bicyclist—-18 reports
Collision at vehicle turn—–12 reports
Bicyclist violated signals—-11 reports
Collision with vehicle door—9 reports
All other circumstances——-4 reports

Factors: Lack of attention by both motorists and bicyclists appears to be a strong factor in the reported bicycle crashes. Frequent circumstances were motorists pulling out into traffic, making turns and opening doors. Motorists were considered at fault in 28 reports, bicyclists in 12 reports and pedestrians in 2 reports. Citations were issued to 21 motorists and to 7 bicyclists.

From these reports alone, one cannot tell whether Brookline streets are relatively dangerous or relatively safe for bicyclists. They do not indicate corresponding bicycle and motor vehicle traffic densities. So far, there is little comparable information from elsewhere in the United States. Informal observations find bicyclists in Brookline stopping more often at traffic signals than those in Boston’s terror zone along Commonwealth Ave.

Other communities: Several years ago, New York City published a multiple-year report on bicycle crashes. It focused on fatalities and “serious injuries” but also analyzed “contributing factors.” This report found the two most common factors were “bicyclist crossing into a vehicle path”–reported for 84 percent of crashes–and “driver inattention” or “driver error”–reported for 60 percent of crashes.

Crashes at intersections were reported about ten times as often as crashes in mid-block. Midtown Manhattan and south, down to Union Square, appears to be the terror zone of New York City. Informal observations often find bicyclists in midtown Manhattan weaving through traffic. Neither Boston nor Cambridge has published detailed information online. Occasional incident maps from those communities provide the few clues.

Improving safety: Reducing bicycle crashes remains an art and a goal in the United States, not yet a science or a record. John S. Allen, a veteran urban bicyclist in the Boston area, has described some efforts in Cambridge. His report on a Vassar St. bicycle lane shows how what might have sounded like a good idea, at least to some, yielded perverse results. It is not clear how thoroughly the Brookline Bicycle Advisory Committee has investigated this nearby experiment.

As of summer, 2014, there are no federal standards for enhanced bicycle markings at intersections. Designs have been promoted by organizations, but they have yet to be validated against alternatives through systematic and prolonged testing. Issues can become complex. Mr. Allen described several he encountered while a member of the Cambridge Bicycle Committee during the 1990s. So far, they do not appear well resolved.

– Craig Bolon, Brookline, MA, August 16, 2014


Daniel C. O’Leary, 2013 bike crashes, Brookline Police Department, February, 2014

Leze Nicaj, et al., Bicyclist fatalities and serious injuries in New York City, NYC Office of Chief Medical Examiner and NYC departments, 2006

John S. Allen, About Bicycle Sidepaths, 2010


Note: Readers who examine Mr. Allen’s descriptions will find he disapproves of separated bicycle lanes, which he calls “sidepaths” and “bike paths” rather than “cycle tracks.” Mr. Allen omits to mention that as a long-distance commuter, between Waltham and Cambridge, he tacitly sides with high-speed bicyclists and against low-speed bicyclists. The former try to maintain around 20 to 30 mph–about 7 to 10 times walking speed–as contrasted with around 6 to 9 mph for the latter–about 2 to 3 times walking speed.

That difference has developed over about the last 30 years here. It has become a major distinction between a typical U.S. and Canadian approach to urban bicycles, tending to favor high-speed bicyclists, as compared with a typical Dutch and Danish approach, tending to favor low-speed bicyclists. Loudmouths and pressure groups among domestic bicyclists represent only high-speed riders. Nearby, one often finds those in the Boston terror zone, B.U. neighborhoods of Commonwealth Ave.

An even more violent scene of the same sort can be observed in Watertown and Cambridge segments of the Paul Dudley White bicycle path, mostly on the north side of the Charles River, around 8 to 9 am on a weekday morning. These days, unlike the 1970s, arrogant high-speed bicyclists dominate the scene, recalling classic, hyper-aggressive “Boston drivers” of the 1950s and 1960s.

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