A review of Cambridge bicycle citation and collision data as they impact bicycle and general street safety planning

Dear Fellow Councillors, I have been working with another bike-safety data nerd, Ted Feldman, to try and figure out how CPD traffic enforcement efforts correlate with bicycle safety to see where enforcement efforts might be altered to improve bike and pedestrian safety. The City has a variety of bicycle safety efforts—from rider education programs in schools to infrastructure changes and DPW’s construction zone hazard management work— but the data that we know exists and to which we have ready access is pretty much limited to data about reported crashes, CPD citations and the ‘bike totem’ bicycle counts. The focus of this particular memo, therefore, is how data analysis might play a role in making cycling safer through more focused infrastructure improvements and more intentional and data-driven traffic enforcement efforts. The majority of reported bike collisions involve some sort of turning movements but bike collision (and near collision) data is very incomplete. Complicating data collection and analysis efforts is the fact that accidents such as falling on ice or hitting potholes, or any of a number of other ways cyclists can get hurt, do not readily fit a ‘crash type’ and are frequently not reported. Still, the chart to the left (Figure 1) shows the types of collisions we have in Cambridge and it reflects data on bike/car collisions elsewhere. One major Figure 1. A chart of the prevelance of crash types. Crashes associated with turning movements and/or intersections account for well over half of all reported crash types. Page 2 of 4

key to making cycling safer in Cambridge, then, is to lessen dangers associated with intersections and turning movements. Accomplishing that goal may be at least partially accomplished through a combination of infrastructure changes like the ‘no left turn’ signs in Inman Square, bike traffic lights, education and enforcement. Based on the fact that so many of our bike citations are at places where there are intersections, CPD seems to be focusing on cyclists running red lights.

It is not clear whether the police are at intersections specifically to ticket cyclists who run red lights or they are there because both drivers and cyclists run red lights and some cyclists wind up getting ticketed just as some drivers do. One thing that the heat map to the right (Figure 2) demonstrates, though, is that our bike citations are concentrated along certain popular bike routes whereas reported bike ‘crashes’ occur all around the city.

If the goal of bike citations is to promote bike safety, we may very well not be giving bike tickets in ways that help meet this goal. A graphic of the timing of bike citations, all traffic citations and bike ‘crashes’ (Figure 3 below) reveals that, while there is not a direct correlation between citations and crashes, there are more of all three during rush hour commutes. Conceivably, there is a link between increased bike, and maybe all traffic, citations and fewer crashes.

If one point of traffic enforcement is to reduce collisions between bikes and cars/trucks, it seems like this is one area in which we need to do a deeper data dive. Guiding this process, we can ask: are CPD’s enforcement efforts, for bike and motor vehicles, most appropriately timed to maximize street safety? It is also clear that CPD gives out very few bike citations after dark.

That makes some sense, as fewer people bike at night, but it does lead one to wonder if we’re putting enough effort into emphasizing the importance of safe biking, especially having front lights, at night. Of course, CPD has other things it does at night, so a discussion of evening/night bike enforcement would also include a discussion of CPD’s overall priorities and nighttime staffing levels.

Figure 2 Locations were bicycles are most likely to receive a bicycle citation (in blue), imposed with locations where bicyclists are likely to be involved in a ‘crash’ (in red). Page 3 of 4

Figure 3 Graph showing the percent of reported bicyle crashes and violations, along with all violations, in Cambridge during the reported period, and the hour in which they were recorded. Commuting hours in the morning and early evening witness increases in both bicycle crashes and violations. While reports of bicycle crashes increase through the evening hours between 6:00 p.m. and 9:00 p.m., the number of citations decreases steadily. Figure 4 Distribution of all citations by violation type. Bicycle violations total roughly 5% of all citations. Page 4 of 4

The chart above (Figure 4) shows that roughly 5 percent of all citations are given to bicycles. I don’t know if that reflects the percentage of bicycles on the road compared to cars and trucks, but I think it is still a pretty big number and I think most cyclists biking in or through Cambridge have some story involving a citation. The problem with bike citations, though, is that other than knowing when and where they were given, we don’t seem to have ready access to knowing why they were issued.

I would like to work with CPD to change the bicycle citation form and related data collection to allow us to readily see which offenses result in citations and which ones do not to help inform other bike safety efforts and our overall street safety work . Similarly, the chart tells us something about what we’re giving drivers tickets for, and things like crosswalk violations, a pet peeve of mine, seem low on the priority list.

Given the disproportionate danger that motorists pose to other road users, to the extent that we can get drivers to pay attention to other people on the road, especially cyclists, I think we’d make great strides in traffic safety. About 40 percent of the drivers’ tickets are given for running stop lights or stop signs while failure to yield is only 5 percent of driver citations even though such failure to yield is very dangerous for cyclists and pedestrians.

Cambridge would be safer if drivers paid a lot more attention to turning safely, whether it is at a street intersection or into a driveway, and I think more intentional enforcement efforts in this area would help make that happen.

Anecdotally, the delivery economy and associated curb access requirements and sometimes unpredictable driving and parking habits of Uber, Lyft, UPS and Amazon drivers have created a new set of safety hazards especially pertinent to cyclists but it is not clear that we do, or can, capture specific data on this specific street safety challenge.

In conclusion, there needs to be a broader and more detailed conversation about bicycle and street safety and equity, reflecting the multi-faceted safety challenges and transportation needs of Cambridge’s streets. Certainly, infrastructure improvements targeting the dangers involved with turning movements and intersections, as well CPD’s traffic enforcement efforts, have a big role to play in keeping all of us- cyclists, pedestrians and drivers- as safe as possible.