Pittsburgh's bike sharing system Healthy Ride opened its 100th station in the city Thursday, at the corner of Penn Avenue and Winebiddle Street in Garfield.

It's a sign of the system's growth; the number of bike share stations have doubled since the system got its start in 2015. Still, a map of the city's Healthy Ride stations show noticeable blank spots in some neighborhoods, incluidng in the West End, South Side Slopes and Upper Hill District.

The reason? Executive Director David White said the main issue is that those areas are very hilly, which means less biking and less demand from residents. The West End has an additional challenge.

"We've got some sections of our city that are divided by multi-lane, fast moving roadways," White said. "We really try to prioritize safety."

White said Healthy Ride chooses its station locations in a collaborative, community-informed way.

"We collected over 800 suggestions for where those stations should go," he said. "And then we use tools to prioritize stations that can connect people to public transportation and to business districts."

Healthy Ride plans to add 75 new stations in spring 2019, which will expand the company's presence in the North Side, Highland Park and Larimer.

After those installments, the company says more than 170,000 city residents will live within a quarter mile of a station. Anyone can submit a comment about the proposed expansion here.