By GERALD NEILY

Here’s the math behind the story in this morning’s Sun about the City’s free water taxi service from Fells Point to Tide Point. Regular daily ridership is “about 90.” The taxi “now runs continuously from 7 a.m. to 7 p.m., Monday through Friday, with departures every 10 to 15 minutes.”

So with the service running twelve hours a day, with four to six runs per hour, that is about 50 to 70 runs per day.

The math: 90 riders/50 trips = less than two riders per trip.

90 riders/12 hours/2 directions = less than four riders per hour per direction

That’s the equivalent of about one full SUV trip per hour – hardly enough riders to stop the sea water from rising.

The City was just awarded a $1.59 million Federal stimulus grant to pay for more winter-worthy boats, pier improvements, and to expand the service to Canton. The City intends to keep the service free as long as the money holds out.