Thanks Frank, for the thoughtful review. It looks like the basis for the BNA model is a good concept, but problematic due to the data source. It might be a matter of time before a better data set is used.
Chip
---- Original Message ----
From: "Frank Gmeindl via Bikeboard" <bikeboard@bikemorgantown.com>
Sent: 12/10/2017 1:43:39 PM
To: "Bike Board - Morgantown" <bikeboard@bikemorgantown.com>
Subject: [Bikeboard] BNA
Here is my take on the People for Bikes Bicycle Network Analysis (BNA) that Drew asked me at the 12/8 BB meeting to write.
The BNA by People for Bikes classifies streets as Low Stress or High Stress for adult cyclists who are interested in riding a bike but concerned about riding in traffic. People for Bikes gives a low stress rating to streets that they think interested but concerned people would probably say they would feel safe riding on. One problem with this approach is that streets that feel safe might not actually be safe, that is, they might actually have more frequent and more severe crashes than other streets that these people feel aren’t as safe. For example, I’ve read countless stories about people on bikes getting killed at intersections by right turning vehicles, especially trucks because the bicycle specific infrastructure led them to be where a competent experienced cyclist would not be, that is, on the right side of right-turning vehicles.
That said, the BNA is a good model for developing good bike route maps because its methodology is transparent, well documented and flexible and they provide the source code.
The BNA provides a map and connectivity scores. The map shows all streets with low stress streets blue and high stress streets red. The connectivity scores include an overall community score, scores for several subcategories such as services, schools, recreation and retail and then scores for sub-subcategories of these that rate how well interested but concerned people can reach these by bike. The BNA enables you to compare communities. The comparative scores can be misleading. For example, the BNA rates Buckhannon, WV higher than Portland, OR, 37 and 33 respectively.
The major limitations of the BNA are its primary data sources: U.S. Census and OpenStreetMap (OSM), and the stress ratings of various street conditions and infrastructure types. The U.S. Census data are only updated every 10 years and do not include sufficient detail to determine number of cyclists and trip characteristics. OSM data completeness and accuracy are questionable. The stress ratings for various street conditions are subjective and biased toward how safe they would feel to interested but concerned people and might be significantly different for competent and experienced bicyclists.
I had fun with the BNA and learned a lot. I’m guessing you’ll have fun with it too. Then, we can discuss how it could inform our bike route mapping efforts as well as our efforts to improve infrastructure and education. But, most of all, I’m looking forward to riding our infrastructure to see how safe it feels while we’re having fun on it;)
Frank