The bus system is one of the amenities the company is using to help recruiting and retention in the face of stiff competition for engineering talent from Google and others. As of last November, average ridership was about 55 percent, and about 15 percent of employees who made reservations didn't show, as we reported in this story at the time.

To date, the Connector system has provided more than 130,000 rides, and it has been used by 4,300 employees, according to the e-mail from Microsoft spokesman Lou Gellos. The company says more than 2,500 of them had been driving to work alone before. It says the system has saved more than 1.3 million pounds of carbon emissions, which Gellos described as the equivalent of turning off electrical power to Microsoft's Building 17, which holds 650 employees, for six months.

As part of the changes announced today, Microsoft is also adjusting and expanding some existing Eastside routes for the convenience of employees. There is no immediate indication that the company is opening the service to contract workers, but I've asked for more information on that and other questions, and I'll update this post with more details.