The April 1, 1907 NYT reports on a day's worth of arresting automobile drivers who were "caught" speeding on Manhattan Island. The story sounds much like This November (1906) story concerning the arrests of drivers in Peekskill, NY. However, the price of a speeding ticket in New York City was considerably higher:

Bicycle Policeman Gibney took Waler C. Martin of 344 West Seventy-seventh Street to the 157th Street Station. He had been timed as going at the rate of twenty-four miles an hour on Broadway...He was released on $100 cash bail. Frederick Lauterback...had been timed as going at the rate of twenty-five miles an hour on Broadway...he was compelled to deposit $100 cash bail before he could proceed.

William Erhardt ...was taken to the 125th street station by Policeman Mara, who timed the car at twenty miles an hour on Broadway. Erhardt gave $100 cash bail.

The story goes on to mention others caught for speeding at 18 mph, 18mph, and 20mph. This might imply a speed limit of 15 mph, but I haven't been able to confirm that.

In November, 1906, a fine for speeding in Peekskill was $10-$25 or $225-$575 in 2005 dollars. The bails in NYC were around $2,100 in 2005 dollars - plus you were embarrassed with the NYT perp walk, which seems eerily similar to the rehab, divorce-court, murder-trial perp walks today's Who's Who endures.