Bryan Bryson can’t recall the exact day it occurred to him there are no bike-share stations around his home near the Ashmont T stop in Dorchester. All he knows is one day, when the Red Line was having problems, he considered using his bike-share membership to bypass the stall.

“I thought, ‘Oh, I’m just going to get off, go find a bike and do the rest of my trip home that way,’" he said. "And then I realized, I couldn’t do that."

Bryson bought a membership for the greater Boston bike-share back when it was known as Hubway. The system underwent a redesign, complete with the new name Blue Bikes, after its four municipalities — Boston, Brookline, Cambridge and Somerville — arrived at an $18 million investment agreement with Blue Cross Blue Shield of Massachusetts.

Until he moved to Dorchester in 2014, Bryson said, he used the public-private bike-share as a quick alternative to gridlock and subway difficulties that can slow or halt a commute.

“I spent so much time living in Cambridge where you could just walk to a Hubway. There was a Hubway where I worked. I took Hubway from one office to the next, and then the idea of having that same type of flexibility to just do a quick trip here or there wasn’t in my neighborhood,” he said. “I couldn’t even tell you, when I first moved to Dorchester, where the closest Hubway was. There was just a point where I was like, ‘Okay, Hubway stops here, and we’ll never see it.’”

Dorchester is home to nearly a fifth of Boston’s population, but only has about a dozen bike-share docks — that’s if you count the southernmost one at the Franklin Park Zoo. The current inventory leaves out neighborhoods farther south including Ashmont Hill, Neponset, Codman Square and Lower Mills as well as the Fields Corner and the Shawmut T stations.

Contrast that situation with where Bryson used to live and now works as a professor of biological engineering at MIT. Cambridge has a slightly smaller population and is slightly bigger than Dorchester, yet has four times more bike stations.

Since the system’s launch in 2011, Cambridge has contributed nearly $3 million to build up bike sharing in the city. Its stations are among the system's most visited, according to a WGBH analysis of 2018 data. Many docks are conveniently located within five-minute walks of each other.

Bryson said the disparity led him to cancel his membership and start using his own bike.

“At some level, you as a consumer can make decisions on what types of businesses to support and endorse, and you can do that with your money,” he said. “If you’re not in my neighborhood, why am I going to pay for this?”

A growing body of research suggests Bryson isn’t alone in noticing that some neighborhoods lack access to bike shares. Nathan McNeil, who studies transportation at the Center for Urban Studies at Portland State University, said cities have tended build their networks like spiderwebs — out gradually from epicenters in downtown areas.

“Often times those end up being higher-income communities and more predominantly white neighborhoods. And many times the lower-income and generally underserved communities were not included in those initial launches,” he said. “And that’s somewhat understandable in the sense that the cities wanted to show that they could be successful from day one. But then, as they started to grow, it became more evident that they weren’t necessarily serving the diversity of the cities they were in.

“The absolute first step in having an equitable bike-share system is that there has to be access to the system. So there has to be bike-share stations in underserved communities,” McNeil added.

Rutgers professor and transportation researcher Charles T. Brown agrees, adding that even after a city begins adding bike-share equipment, more work is needed to address usage barriers and achieve bicycle equity.

“One of the things that is very, very important [is] there needs to be a prioritization of bicycle infrastructure in the poor areas of town. Too often, stations are placed there, yet the overall transportation network isn’t conducive to safe and comfortable bicycling,” he said, adding that outreach is crucial to getting community buy-in.

“Too-often bike-share companies assume that all of the population knows what a bike-share system is, knows how to use it, and thus don’t put up the necessary resources in the beginning to properly educate the community in regards to the existence of a system, and then how to properly access and utilize that system,” Brown said.

Stefanie Seskin, active transportation director for Boston, said the city is working towards bike-share equity on both fronts. She points to various programs like reduced-price Blue Bikes membership, summer Boston by Bike rides and free learn-to-ride classes as ways the city is trying to foster equity.

She acknowledged Boston has expanded at a slower pace than some cities and admits the downtown-focused network has made reaching outlying communities a challenge.

Seskin said she also understands why people like Bryson cancel their memberships when the system doesn’t serve where they live.

“I understand that frustration for sure. It is definitely something that we have been really focused on doing — getting that funding so that we can grow in southern Dorchester and Mattapan and Rosalindale, which are neighborhoods that have been very vocal about wanting more transportation options and wanting to be able to ride on a bike in our bike-share system,” she said.

The system currently has nearly 200 docks, up from 60 in 2011. The latest round of expansion is set to start next month and will include 50 stations in Boston. Seskin could not say precisely how many will be in southern Dorchester or Mattapan, which has no bike-share docks.

Bryson is waiting to find out where the new ones will be. He said he still sees biking as a social activity and wants to support the bike-share system when it comes to his neighborhood.

“I just think we’re honestly ready to be able to experience the neighborhood the same way a lot of other people elsewhere across the city experience their neighborhoods: on a bike and through active transportation," he said.