The City of Cambridge has moved forward with a plan to ban all left turns in Inman Square, a step the Bike Union advocated for in order to make the intersection safer for all users. This is one of several “rapid response” interventions Cambridge is implementing after the fatal crash in Inman that took the life of Amanda Philips back in June. The intent of rapid response interventions is to immediately make an intersection less dangerous for everyone using it, with particular attention paid to protecting vulnerable road users.
Cambridge’s Bicycle Plan highlights left-hooks as one of the City’s top three most prevalent types of crashes that lead to bicyclist injury. In addition, their bike crash map shows left hooks as the leading type of crash in the Hampshire – Cambridge Street intersection. Besides the universal reasons why left turns are more dangerous – they require a lot of focus in looking for oncoming cars and a crosswalk that is farther away, often there is pressure from behind to “get out of the way” and make turning movements as quickly as possible, and when cars are queued up coming from opposing directions, both waiting to turn left, sight lines for all are significantly obscured – the length and geometry of Inman Square make left turns in the intersection particularly dangerous. Even if cars re-route and make left turns in other intersections (Prospect and Hampshire or Prospect and Cambridge), those intersections are much more compact, and the City may have the opportunity to experiment with protected left turns and other signal timing changes if needed.
Cambridge is not alone in taking measures to reduce the danger of motor vehicle left turns. A study produced by the NYC DOT uncovered a disproportionate amount of pedestrian and bicyclist injury and death caused by left turns. NYC DOT has already begun experimenting with changes to intersections troubled by left turns, with demonstrated results: their data shows that turn restrictions led to a 41 percent reduction in left turn-caused injuries to bicyclists and pedestrians over the course of three years. (Not insignificant, this study also showed that protected bike lanes led to a 15% reduction in left turn injuries.) Based on this research and what we know about the current conditions, we anticipate this ban will lead to a significant increase in bicyclist safety as the city works on a more permanent solution to fix Inman Square
At the July 19th Cambridge City Council Hearing on bike safety issues, when urged by the Bike Union and others to consider restricting left turns in the intersection, Councilor Jan Devereux proposed a motion to ask the transportation staff to look into the ban. We’re celebrating this advocacy win – we fiercely advocated for this measure – and are glad to see the City willing to try something to see how it works, rather than belabor what the impacts might be ahead of time. We hope that there is a fair amount of enforcement as soon as this sets in, so people understand their patterns may have to change. We appreciate that the city is ready to watch, learn and adjust — a great attempt at being nimble.