Google engineers who built the company's new bicycle route mapping service didn't need to look far for inspiration.

The team is based at the Fremont office right alongside the Burke Gilman Trail. This screenshot of the bike route feature shows the office at left:

Bike commuters at Google offices around the country helped the Seattle-based team build and refine the new feature for Google Maps, which is launching Wednesday. That coincides with the National Bike Summit cycling advocacy event this week in Washington, D.C.

The small team built the feature in just five months, adding a new map layer that provides suggested routes for bicyclists in 150 cities across the U.S. It joins the walking and transit directions already provided by Google.

It also comes as maps move to the forefront of the battle between Google and Microsoft. Mapping underpins new locally targeted advertising efforts that may provide the next wave of growth for the search giants, especially as more computing's done on mobile devices that transmit users' location.

Google's bike routes come a Microsoft's been raising the profile of Bing Maps with demonstrations of "spatial search" technology that blends public photos of places with map imagery to make its maps more immersive.

The "Bicycling" layer coming to Google Maps isn't a technological tour de force but it looks like a fun and useful feature for cyclists, especially those visiting a new area and looking for places to ride. It's also been the most requested addition to Google Maps, with an online petition calling for bike routes drawing more than 50,000 signatures.

Google worked with the national Rails to Trails Conservancy to add the group's trail maps, combining them with publicly available bike route information.

But the maps are still incomplete. Google's hoping users will help fill in the gaps, suggest routes and make corrections using the "report a problem" feature.

"We really are thinking of all this data as a starter set," said Shannon Guymon, project manager for driving directions and lead on the bike routes.

Maps display three tiers of bike routes - bike trails such as the Burke Gilman, dedicated bike lanes on streets and roads, and roads without bike lanes that are appropriate for biking.

Routes aren't necessarily the most direct. The system factors in topography and the amount of energy a rider would need to reach the destination.

In other words, it has a built-in hill avoidance system. Comments added to the code by Andy Schwerin, a former Google engineer who started the project before leaving for a startup, include formulas for calculating the energy used by cyclists.

Google tuned the system conservatively, to provide relatively easy routes for people. That's drawn some flak from hardcore cyclists at Google who tested the system.

"Sometimes we get feedback from Googlers who say 'you should take this one, it's faster,' but they're more aggressive cyclists than the style we're targeting," Guymon said.

Users can adjust the suggested routes by clicking and dragging them to different roads or trails.

Google's still working on a mobile version. Later the company may incorporate information about services, such as bike shops along suggested routes.

"We are hoping by launching this feature we encourage more bike riding," Guymon said. "Giving this data on the maps makes it seem more accessible."