Since 2010, rapid bus service has been running on Manhattan’s First and Second Avenues. By nearly all accounts, it’s been a success. Bus speeds are up 15 percent. Faster trips mean that the M15 has defied the trend of sinking ridership on Manhattan buses, adding 4,000 more passengers per day.

But the bus could be running even more quickly and smoothly. When M15 Select Bus Service started running a year and a half ago, the Department of Transportation hadn’t yet installed the full package of improvements for the corridor. Two features in particular were scheduled to be added as follow-up items: bus bulbs and transit signal priority.

A presentation shown to the project’s community advisory committee last April promised that both those improvements would be added starting in 2011, with the installation of bus bulbs continuing through this year. That hasn’t happened yet, a DOT spokesperson confirmed, though the wait for further enhancements may not be much longer. DOT said the bus bulbs would be fully installed by the end of this year, but did not comment on the timeline for signal priority.

Once completed, the two improvements will make traveling on First and Second Avenue even better. Bus bulbs — sidewalk extensions into the street at bus stops — keep bus shelters and ticket machines out of the way of pedestrian traffic. And by allowing buses to load passengers without having to pull to the curb and back into traffic, they also make for faster rides. The MTA has estimated that adding bus bulbs would shave about 10 seconds off each stop along the planned Nostrand Avenue SBS route in Brooklyn.

Transit signal priority, planned for the M15 between Houston Street and South Ferry, gives buses approaching intersections a little more green time. The MTA predicted that signal priority would save Nostrand Avenue bus riders another half a minute for every mile they travel.

Those kinds of time savings, which add up quickly over a year’s worth of travel, are better late than never.