Day: 2017-06-16

Evaluating the Safety In Numbers effect for pedestrians at urban intersections

| David Levinson

Recently published:

Average annual 6-hour pedestrian count by location, Minneapolis
Average annual 6-hour pedestrian count by location, Minneapolis

Highlights

  • Collision risk at 448 intersections in the city of Minneapolis, MN was assessed.
  • The Safety In Numbers phenomenon was observed for both pedestrians and cars.
  • Maps of per-pedestrian crash rates inform discussion of safe vs. unsafe city areas.

Abstract

Assessment of collision risk between pedestrians and automobiles offers a powerful and informative tool in urban planning applications, and can be leveraged to inform proper placement of improvements and treatment projects to improve pedestrian safety. Such assessment can be performed using existing datasets of crashes, pedestrian counts, and automobile traffic flows to identify intersections or corridors characterized by elevated collision risks to pedestrians. The Safety In Numbers phenomenon, which refers to the observable effect that pedestrian safety is positively correlated with increased pedestrian traffic in a given area (i.e. that the individual per-pedestrian risk of a collision decreases with additional pedestrians), is a readily observed phenomenon that has been studied previously, though its directional causality is not yet known. A sample of 488 intersections in Minneapolis were analyzed, and statistically-significant log-linear relationships between pedestrian traffic flows and the per-pedestrian crash risk were found, indicating the Safety In Numbers effect. Potential planning applications of this analysis framework towards improving pedestrian safety in urban environments are discussed.

Keywords

  • Pedestrians;
  • Safety;
  • Collisions;
  • Urban planning

Street wars 2035: can cyclists and driverless cars ever co-exist? | Guardian Cities

| David Levinson

Laura Laker at Guardian Cities writes: Street wars 2035: can cyclists and driverless cars ever co-exist? | Guardian Cities

“Driverless cars appear unstoppable – except of course you can simply walk in front of one and force it to brake. Could this conundrum eventually mean a return to a dystopian world of segregated urban highways?”

I was interviewed, my quotes below …

A visualisation of data captured by an autonomous vehicle. Photograph: Elijah Nouvelage/Reuters
A visualisation of data captured by an autonomous vehicle. Photograph: Elijah Nouvelage/Reuters

Or how about prosecuting pedestrians or cyclists who get in the way of driverless cars? David Levinson, a professor at the School of Civil Engineering at the University of Sydney, is broadly supportive of AVs, but says: “It’s very big brother like, there’s a question of safety v freedom. How much risk to endanger yourself are we going to let you take?”

Thinking back to the kids stopping driverless cars on our imaginary future street, Levinson sees a future where blocking a driverless car could even be criminalised. “The car has a camera and the picture will be sent to the police department, and the police department will come and arrest you for annoying an autonomous vehicle.”

Given these challenges, experts including Hickman and Levinson believe segregation and AV-only roads are inevitable. But wouldn’t that risk a return to the urban dystopia of the 1960s and 70s, when planners crisscrossed cities with elevated highways and erected barriers around roads with the aim of improving safety? The unintended consequences were fast, aggressive driving, and the splitting in two of countless communities.

“I think there will be some roads that will be transformed to higher speed roads,” says Levinson. “I’d be sceptical of someone who says we will not do any of that. But if you can move traffic away from the lower speed streets that pedestrians and cyclists want to use, that’s an improvement.”

Hickman believes “the case is overwhelming against AVs” but fears the powerful motor industry lobby means there is so much private and government money already at stake that the rise of driverless cars would be hard to stop.