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Comment by salmonellaeater | Hacker News Reader

In Seattle a few intersections have been singled out as the most dangerous for cyclists because of the number of collisions involving cyclists there. Considering they are also the highest-traffic intersections for bicycles, it doesn't actually say anything about how dangerous they are per cyclist-trip.

Crashmapper is useless without knowing how many vehicles pass each intersection per day.

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However, if you want to use it to know where to focus efforts to save the most lives it is useful. It's the correct representation for some uses, just not for all uses.

Although even in that case it's important to know both pieces of information. Past some level of safety, intersections likely hit a floor where no amount of further investment will actually make them safer.

> Past some level of safety, intersections likely hit a floor where no amount of further investment will actually make them safer.

That point is probably called "driverless cars."

And "driverless cycles" probably also.

That data is easy to sample if necessary, whereas the crash data is not.

Useless for figuring out how absolutely safe an intersection is by specific mode of transit at a specific point in time, sure.

There are other uses though, you just have to make sure to take into account the unknown denominator. That's why being able to compare layers and run through time is so important.

Right. For example, if your goal is to reduce total number of crashes, (assuming you are in a position to meaningfully impact this,) the ability to identify "hotspots" is extremely valuable.

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