I can't help you find all the data you're looking for, but my guess is that you're curious about whether Mayor Bloomberg's administration is massaging some numbers [http://www.nyc.gov/html/dot/html/safety/safety.shtml], in which case, you may not have to go back all the way to 1910.

You can find fatality data going back to 1975 online using FARS, the National Highway and Traffic Safety Administration's "Fatality Analysis Report System encyclopedia." It's at: http://www-fars.nhtsa.dot.gov/Main/index.aspx.

To find NYC's vehicular fatalities (which includes non-motorists and motorists involved in vehicular crashes), you can build queries for individual years using the "query" tab. To get data for just NYC rather than the whole state, you'll need to (a) check the "city" box in Step 2 of your query, and (b) include the city code information in Step 3 of your query. The code for NYC is 4170.

For 2007, if you choose data for number of PERSONS, rather than number of CRASHES, you'll find that you get a figure of 776. Whereas choosing data for the number of CRASHES will give you a figure of 263--a value that's closer to Bloomberg's (not sure what he's counting as New York City--FARS data for 2007 is divided into Bronx, Queens, Richmond, New York, Kings).

Whether these figures still follow his math in terms of drops in fatalities is something I'll leave to you.

Rather than running individual queries, you might want to ask the nice folks at FARS to respond to your specific query: http://www-fars.nhtsa.dot.gov/Requests/DataRequests.aspx. They can at least do so for the years from 1975 onward.

As you can see on that contact page, you can also download all the data from their ftp server and number crunch to your heart's content, but it might be a time-intensive process to sift through it all to find what you're looking for.

I hope this helps you.