Cities across the country looking to boost their transit options are giving special fast bus routes a fresh look — an effort buoyed by hundreds of millions of dollars in coronavirus relief funds that could get another boost if Congress passes an infrastructure package.

The Federal Transit Administration last year awarded $375 million to help build the lines, known as bus rapid transit (BRT) — the largest sum in a decade, according to agency records.

In a pipeline of almost 50 transit projects seeking federal investment in the coming years, 34 are for the bus lines. Eighteen projects under construction or in planning phases shared $185 million in funds from the most recent coronavirus relief package.

The lines take the humblest form of public transit, the city bus, and supercharge it using a combination of technology, road redesigns and route planning tweaks. The bus projects are gaining steam as federal transportation officials prioritize modes of transportation seen as more friendly to the environment in a battle against climate change.

Some transportation experts are skeptical because many lines that are dubbed BRTs involve only limited upgrades to bus service. They say those kinds of lines are not likely to tame urban sprawl or lure suburban drivers out of their cars.

Many of the projects are in major cities and have costs in the hundreds of millions of dollars.

But transit agency leaders say the advanced bus lines — with the prospect of driving local economic development in ways regular buses struggle to do — are particularly appealing in smaller urban areas and the less dense communities that dominate the American landscape where subways and light rail lines are hard to justify.

(Here in Atlanta, MARTA has several BRT projects under consideration or on the drawing boards.)

Some warn that betting on a form of transit well suited to America’s road-dominated cities and suburbs could be counterproductive: an unhappy middle way that offers modestly better service and does not promote the kind of denser communities that allow transit to thrive.

The Federal Transit Administration has adopted a broad definition that encompasses projects that upgrade a transportation corridor but do not necessarily have dedicated lanes or roads for the buses.

Annie Weinstock, president of consulting firm BRT Planning International, said the label should apply only to lines that fit specific criteria: The buses have their own lanes or travel on dedicated roads; passengers pay their fare before they board; stations have raised platforms so there is no need to step up onto the bus; and intersections are designed to prioritize bus movement.

Ian Duncan writes for The Washington Post.