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Mapping Nashua’s Bike and Ped Accident Data

A picture emerges of opportunities for improvement.

As an engineer I like to base my opinions on solid information.  I could go to various government agency websites and get facts and figures, but without context it doesn’t mean very much.  Since I am interested in affecting local change, I wanted to see how dangerous Nashua streets are for pedestrians and cyclists.  I didn’t find any data broken down in any useful way, so I contacted the information specialist at the Nashua PD and asked them for the data they had on accidents.   They were very helpful, and after a few back-and-forth emails, I got an Excel file of all motor vehicle accidents in Nashua for the last 5 years, when their current system started tracking them.  Now I had something to look at.

But how to look at it?  Pictures are nice, so how about putting it on a map?  I looked at various mapping sites and found that for something simple like this, Google makes this very easy and, even better, free!  I won’t dwell on it too much but being a software engineer it was simple to write a small Python script to read the Excel file, extract just the useful columns, convert some numerical type codes (for example, car, pedestrian, bike) into readable words, and normalize the addresses.  Since it was only Nashua, the Excel file didn’t include the city and state, but when using the geolocation in Google it searches the entire world.  There are a lot of “Main Streets” in the world.  The script also output the data as a CSV file which was easy to import into Google.

Now that it is in a Google map it is easy to zoom around and see where the trouble spots are.  You can also select “just pedestrian” or “just bike” related.  As expected, most of the accidents are where the people are, like the downtown or in areas that were designed with only cars in mind like Amherst Street and South Daniel Webster.  Of course, the data set is limited in many ways because it doesn’t indicate the severity of the injuries, if any, and it only includes those motor vehicle accidents that were reported to the police.  There are probably more that go unreported, but I have no idea how to find that out.  I would also like to contact the fire department and see if they have similar pedestrian or bicycle injury data.  I suspect they would receive even fewer reports but might have an indication of the number of serious injuries.

I did this to answer my own questions about my own community.  I found that the City agencies like police are very willing to help with this data.  Putting data on a map is a powerful way to convey where and how much danger cars pose to people in the community.  Once we have this data we can both use it to advocate for change and to measure progress for the changes we make.

I hope others can use my map here to inspire them to look at their own communities.