Maryland Gov. Larry Hogan (R) is debating whether to approve or cancel Baltimore’s $3 billion Red Line light-rail line and suburban Washington’s $2.5 billion Purple Line. His administration has suggested he might approve these lines if the costs can be reduced. Here are five things he needs to know before he makes his decision.

1. No matter how much they say light rail will cost, it will always cost more. Department of Transportation reviews of projected and actual rail transit construction costs have found that almost all rail projects cost far more than projected, with average cost overruns of 50 percent and overruns on many recent projects of more than 75 percent. Rail planners also consistently overestimate ridership by an average of 70 percent.

2. Claims that light rail will pay for itself by generating new taxes from economic development are pure bunk. FTA-funded research has shown that “Urban rail transit investments rarely ‘create’ new growth, but more typically redistribute growth that would have taken place without the investment.”

Worse, the tax burden required to pay for rail transit can actually slow economic growth: on average, urban areas that spent more on transit improvements in the 1990s grew slower in the 2000s than ones that spent less. Not only will there be no new taxes to help pay for the rail lines, rail construction will pose an especially heavy burden on Baltimore, which doesn’t need another obstacle to urban recovery.

3. Maryland couldn’t afford to build new rail lines even if the construction cost were nothing. Existing transit lines in the Washington and Baltimore areas suffer from multi-billion-dollar unfunded maintenance backlogs. The problem is especially acute in Washington, where a 2009 crash that killed nine people and a 2015 incident of smoke in a tunnel killed one person can be directly traced to inadequate maintenance.

Instead of rehabilitating existing lines, northern Virginia is spending $6.8 billion on a rail line to Dulles International Airport; the District wants to spend $1 billion on clunky streetcar lines; and some people want to spend $2.5 billion on the Purple Line. It makes no sense to build more rail lines that taxpayers can’t afford to maintain when the existing lines are falling apart.

4. Transit riders care more about frequencies than whether their vehicle is a bus or railcar. Maryland can do a lot more for transit riders at not much added cost by simply running buses on existing streets on light-rail schedules — that is, more often and with fewer stops.

As Undersecretary of Transportation Peter Rogoff has discovered, “you can entice even diehard rail riders onto a bus, if you call it a ‘special’ bus and just paint it a different color than the rest of the fleet.” Such special buses, Rogoff adds, “can move a lot of people at very little cost compared to rail.”

5. Buses can move more people faster, safer and for far less money than light rail. The “light” in light rail refers not to weight but to capacity: light rail literally means low-capacity transit. Buses can move more people per hour on city streets than light rail, and because buses can go anywhere the streets go, more people can reach their destinations without having to transfer between buses and railcars.

The Baltimore Red Line is projected to have an average speed of less than 19 miles per hour, while the Purple Line will go less than 15.5 miles per hour. Both lines are expected to increase, not reduce, traffic congestion. On average, light rail accidents also kill almost three times as many people, per billion passenger miles carried, as buses.

Building these rail lines would have the same economic effect of digging two giant holes in the ground and filling them up again. A few people might be grateful for getting jobs digging holes, but everyone else would be burdened by the cost and would get nearly no benefits from the projects. Let’s hope Hogan understands these facts when he makes his decision.

The writer is a senior fellow with the Cato Institute and a visiting fellow with the Maryland Public Policy Institute.