Friday, July 17, 2015

In 2013 there were 458 bicycle crashes in Miami-Dade, up from 234 in 2005

A highly interesting read by Sebastien Lozano & Matthew Toro in Miami Geographic. The numbers appear alarming however the bike culture in Miami has increased greatly along with the population. The article includes 'heat maps' that indicate where the accidents are clustered and you can see the trends over time. The FDOT is very precise with their data in Miami-Dade and wonder if this data is statewide or just for that particular city.

Remember some time ago hearing someone state that West Palm Beach's emphasis on bikeability was going to greatly increase bike accidents and make the public there less safe. There is a calculation that is cited in the article that debunks that notion:
"Taking into account the amount of walking and bicycling, the probability that a motorist will strike an individual person walking or bicycling declines with the roughly −0.6 power of the number of persons walking or bicycling. An individual’s risk while walking in a community with twice as much walking will reduce to 66% (20.4/2 = 2-0.6 = 0.66)."
As the authors explain, if West Palm Beach were to increase its bike ridership by 100% the number of accidents would be projected to increase 33%, not 100%.

Here are two excerpts from the article:
     With regard to the specific neighborhoods most affected by automobile-on-bicycle collisions, one area in particular stands-out as a constant hot spot during the nine year period. Miami Beach is where crashes are overwhelmingly densest.
     The central and southern parts of Coral Gables, near the University of Miami, as well as the City of Miami proper, also experience consistently high crashes levels. Neighborhoods such as Little Havana, Brownsville, Overtown, and central downtown have relatively high crash counts and density levels. On the other hand, some neighborhoods experience relatively fewer crashes. The relationship between neighborhood population density and bicycle crash density is apparent.
[and. . .]
     Does this mean it’s becoming even more dangerous to ride a bike in Miami? Not necessarily. [emphasis added]
     That conclusion can’t be made with crash data alone. What’s more important is the ratio of bike crashes to overall bike ridership. It’s plausible that the near doubling of crashes from 2005 to 2013 is due simply to more Miamians taking to the streets on their own two pedal-powered wheels. Without question, the cycling culture in Miami has grown in the last several years, as exemplified by the explosion in popularity of Miami’s monthly Critical Mass event.
Here is an example of a 'heat map' created by the authors to show the clustering of bicycle accidents: