SL1: 128 trips weekdays, 99 Saturdays, 126 Sundays.

SL2: 142 trips weekdays, 75 Saturdays, 70 Sundays.

SLW: 67 trips weekdays.

Last week, I was quoted in the Globe (*) about the travesty that is the D Street light . The city has said they've fixed it, but they haven't, because oh noes, cars might have to wait! So buses still wait at a 100-second-long traffic light for a green signal. Apparently they tried transit priority and it didn't work (which is a pitiful excuse; it's proven technology) and gave up. So we're back to square one.Now, there's a lot of discussion about the T's huge deficits and the need for fare hikes , but this sort of low hanging fruit is apparently anathema. I've calculated it out before, but here is a quick sketch of how much money could be saved in operational costs by having a working transit signal preemption at D Street. One caveat is that at rush hour there might actually be enough bus traffic that signals might not be able to let every bus through at speed: there are 30 buses per direction per hour, so one bus per minute, and the cross traffic needs at least, say, 20 seconds for a pedestrian signal. But given that the current average delay, with deceleration and acceleration, is one minute, even 20 seconds is a heck of a lot better.Let's say that the average bus experiences a 45 second delay (this is conservative, especially since schedule padding is required based on the longest time possible to wait, more than three minutes per round trip, or nearly a quarter of a Silver Line Waterfront round trip). For the Silver Line Waterfront shuttle from Silver Line Way to South Station, this accounts for 10% of the total run time, for the SL2 it's 7% and for the SL1 4%. How many trips are affected? Based on recent schedules:Total: 337 trips weekdays, 174 trips Saturdays, 196 trips Sundays. Or 2055 trips per week. And these are one-way trips, so actually 4110 trips per week (this will go up once Silver Line Gateway service begins running). Assuming that each of those trips loses 45 seconds, we're talking about 3082.5 minutes of operating time per week wasted sitting at the D Street light, or 51.375 hours per week. 52 weeks in a year gives you 2671.5 hours of savings, and at $163 per hour (the cost in 2013 to run a T bus) the cost savings amount toper year. It's probably higher by now.Let me repeat that: by fixing D Street, the T could operate the exact same amount of service on the Silver Line, but cut costs by nearly. The argument that it would just be built in to schedule padding is spurious, since a more predictable light would save considerably more time, and the run times are short enough that the same amount of service could be operated with fewer vehicles, or the same vehicles could run more frequently. (For instance, if the Silver Line Waterfront service time went from 15 minutes to 13.5, a bus could make 9 round trips in two hours instead of 8.)If the FMCB is serious about cutting costs, they should be banging down the doors at BTD for this sort of common sense solution to save money. There's no need to cut service; in fact this would increase service quality. Yet everyone is content to pass the buck, and years later, service never improves.