Regarding the comparison likely because the data source only gave homicides per ride and didn't come with the corresponding information to convert that into hom

Regarding the comparison likely because the data source only gave homicides per ride and didn't come with the corresponding information to convert that into homicides per person year of use. The choice of 500 is a bit of an arbitrary example of what the latter might look like (~2x per workday). What they really want to compare is per equivalent trip in the city (same mileage, same path, same time) but that's a bit impossible to do directly. Showing the number for going to work and back every day for a year is 1/10th that of traffic deaths in NYC as a whole gets the same idea across despite the lack of precise data anyways.