The Complicated Realm of Collision Data: A Case Study of York Blvd

York Bl east of Figueroa, as seen prior to installation of bike lanes in 2014

In the Bicycle Program, part of our job is to make streets safer and more pleasant for bicycling. We realize that as more and more Angelenos are riding their bikes to get around, there may be more opportunities for conflicts between modes on our streets. Some, if not most, conflicts can be partially addressed by engineering and planning, but part of equation remains in individual motorist or bicyclist behavior.

Regardless of what causes the conflicts on our roadways, it is helpful to analyze available collision data to inform us where there is room for improvement, whether it is behavioral or infrastructural. Two years ago, we took a look at collision data on York Boulevard and found that overall crashes decreased 23% between Eagle Rock Boulevard and Avenue 55 after a road diet was implemented on that segment of the street. In this post we will take a follow-up look at the updated data, and get into the details of who has been identified in the data as “at fault” and the causation of bicycle-car collisions.  The data we are looking at analyzes the 3.9 mile long segment of York Boulevard between Aguilar Street and Arroyo Verde Road over a 12 year period.

If one wants to look at crash data anywhere in California, the primary repository is the SWITRS database: the Statewide Integrated Traffic Records System. All reported collision data is gathered by the California Highway Patrol (CHP) and made available for query.  CHP collects data from local jurisdictions (in our case, LAPD) and adds it to the statewide database, and all data is made available through the California Public Records Act, which requires all records processed by State government to be publicly accessible. Normally, the data lags about 2 years, but SWITRS remains the most comprehensive data tool available to perform collision analysis over time.

Collision data in California are pared down to manageable categories, which makes it great to track overarching trends, but leaves much to be desired in terms of understanding conditions of collisions and nuances of behavior (two of the most important aspects of planning for safer road configuration and design). In the data, there is always a party determined to be “at fault” and a short list of causes, known as the “collision factor.” A cursory glance at the raw data would make anyone’s head spin: ROW Ped, Party 1 at fault. What does that MEAN? While it may seem confusing initially, SWITRS has a codebook that elaborates on what such terms mean. ROW is an abbreviation for “right-of-way,” and Ped is short for “pedestrian.” What ROW Ped refers to is when someone fails to yield right-of-way to pedestrians or other legal sidewalk users, such as people bicycling. Even terms like “Party 1 at fault” can be intuitive with a little context. Every traffic collision typically involves at least two “parties” and differentiating the people involved entails calling the various parties involved Party 1, Party 2, etc.

In this analysis, we attempt to decode this data.  Though, notoriously, car-bicycle collisions that do not result in a “Killed” or “Severely Injured” person are not reported (which always presents a significant data challenge), we will try to interpret a better understanding of what is really at work in the history of car-bicycle conflicts, with York Boulevard as our case-study.

The Overall Picture

Between 2001 and 2012, there were 39 collisions on York Boulevard involving both people driving and bicycling (SWITRS). Those driving were deemed “at fault” approximately 56.4% of the time, accounting for 22 of the collisions that occurred. Meanwhile, people bicycling were “at fault” in 41% of the collisions, deemed responsible for 16 of the collisions that occurred. In one case, the stated collision cause was “other improper driver,” placing neither party involved – the person bicycling nor the one driving – “at fault” (which accounts for the remaining 2.6%)

The primary cause of collisions on York Boulevard over this time period were:

  • Failure to Yield Right-of-Way (11 collisions). This kind of collision is one in which a motorist or bicyclist fails to let the person with right-of-way proceed. An example of this might be someone attempting to make a left turn and not waiting for through traffic to clear in order to safely proceed.
  • Traveling Wrong Way (10 collisions). This kind of collision results from someone driving or bicycling in the opposite direction of the flow of traffic on the street. An example of this could be a person bicycling in a bike lane in the direction opposite to the directional arrow indicated in the bike lane. This does not apply when a person is bicycling “against the flow of traffic” while on the sidewalk.
  • Improper Turn (6 collisions). An improper turn can occur when someone fails to turn according to law, safely, on a green light or when someone makes a right turn on a red without coming to a full stop and yielding to pedestrians and cross-traffic.

The most common reasons people driving were at fault were:

  • Failure to Yield Right-of-Way (10 collisions)
  • Improper Turn (6 collisions)
  • Other Hazardous Movement (2 collisions). This violation is one that may not perfectly fit in a specific category but is illegal and dangerous.

The most common reasons people bicycling were at fault were:

  • Traveling Wrong Way (10 collisions)
  • Other Hazardous Movement (3 collisions)
  • Failure to Heed Stop Signal / Failure to Yield Right-of-Way (each 1 collision). A failure to heed a stop signal can occur when someone runs a red light without stopping or waiting for a green light.

Of the 39 crashes during this time, 7 of them were hit-and-runs, meaning nearly 18% of people driving involved in collisions illegally fled the scene. It should be noted that after the segment of York Boulevard between Eagle Rock Boulevard and Avenue 55 was reconfigured in 2006 hit-and-runs decreased by 38%, a welcomed indicator of the safety benefits roadway redesign can provide. Though recognizing that hit-and-runs cannot be fully eliminated through design, there is currently legislation being considered to address the other side of the coin- enforcement. Assemblymember Mike Gatto has introduced a bill, AB8, which if passed would create an emergency “yellow alert” system for reported hit-and-runs utilizing messaging boards. To further assist in tackling the hit-and-run crisis, our local Los Angeles City Council passed a standing reward program that will automatically award someone who can provide information leading to identifying hit-and-run criminals. All these efforts combined will hopefully result in fewer hit-and-runs regionally.

Collision Hot Spots?

Fourteen of the collisions that occurred along York Boulevard over this time period appear as isolated incidents, with no other bicycle-car collisions occurring at the same place. Seven intersections saw two bicycle-car collisions. In all, 71% of crashes occurred at intersections with only 1-2 crashes. Based on the data, here are some intersections of note:

  • York Blvd and Milwakee St: The intersection of York Blvd and Milwaukee St was the site of four bicycle-car collisions. Two of the collisions were attributed to people bicycling against the flow of traffic while the other two simply state an “other hazard” was at play.
  • York Blvd and San Pascual Ave: Also accounting for four bicycle-car collisions was the intersection of York Blvd and San Pascual Ave. Here there were two primary causes: failure to yield right-of-way and people (in one case driving and the other, bicycling) running a red light.
  • York Blvd and Ave 63: This intersection saw three crashes: two collisions caused by improper turns and another resulting from failure to yield right-of-way.

Bike lanes extending east of N. Figueroa St. were installed in 2014, as seen here between Figueroa and Avenue 63

Looking Ahead

As we continue to monitor collisions in our project areas, it is important to consider the three E’s: Engineering, Enforcement, and Education. Providing designated space for all road users through engineering can make streets physically safer, more organized, and more predictable for motorists and people on bikes. Infrastructure influences how we behave, and when it comes to bicycling, dedicated infrastructure such as protected bikeways have been demonstrated to reduce sidewalk riding, and improve compliance with stop signals.

However, as our bikeways network becomes more robust, we must remember that building bikeways facilities is only a portion of creating safer streets for all users. Behavior shifts through education of all users and enforcement of the rules of the road are also integral to protecting our most vulnerable users.  Working collaboratively with educational outlets such as schools and local advocacy groups to ensure people on bikes know how to safely navigate the roads, updating educational resources for people driving, and creating mechanisms that correct poor individual behavior are all strategies and partnerships that should be developed to create a safe and welcoming travel environment on our neighborhood corridors.

The Data

Our data comes from SWITRS.

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