BART is taking steps like erecting higher barriers at some station concourses, making them harder to jump. The district is also installing signage and floor decals informing riders they may have to provide proof of payment and warning them against fare evasion

Those are peripheral measures. The heart of the anti-fare-cheating effort is a proof-of-payment system that will require passengers to show a valid Clipper Card or ticket, on demand, when they're inside a station's fare gates or on a train.

The system, similar to those already in place on Muni and Caltrain and many other systems, will rely on a half-dozen inspectors, working in teams of at least two, to check fares.

The proof-of-payment rules require a non-biased approach to enforcement: Inspectors carrying card readers will be required to move through an entire car or down an entire platform, moving person to person without skipping anyone, to check fares. That protocol is designed to prevent targeting of individuals based on appearance, age or behavior. To ensure the protocol is followed, fare inspectors will wear body cameras to record their enforcement efforts.

The inspectors will be BART Police Department employees, but not sworn officers. BART police are also empowered to demand proof of payment if officers have "reasonable suspicion" that someone has entered a station's paid area without paying or any time they approach an individual patron on suspicion of some other criminal act.

What will happen if you can't prove you've paid to get on a train?

The first two offenses in any 12-month period will result in a non-criminal citation and fine of $75 for adults and $55 for minors. Adults who rack up a third offense in that 12-month period will face a possible criminal citation and a fine of as much as $250. Minors, who under state law may not be given a criminal citation for fare evasion, would face continued lower-level fines.

The district's fare-evasion ordinance, which formally takes effect Jan., 1, also allows all minors and low-income adults to perform community service in lieu of paying the fines.

While BART police may start enforcing the ordinance on New Year's Day, agency spokesman Jim Allison said last week that the new inspectors were still undergoing training and "are expected to begin their patrols in mid-January."

He added there will be a grace period of at least two weeks during which inspectors will hand out warnings to those who can't produce proof of payment.

One final note: How much difference will six fare inspectors make in a system that includes 45 stations and carries hundreds of thousands of people each weekday?

It's too early to say, clearly. A BART board presentation suggested that fare inspections, along with measures like higher barriers and better video monitoring, could recover $8 million to $11 million a year -- a substantial and welcome sum to an agency that considered eliminating service hours this fiscal year because of an expected deficit.

We'll have a better answer about how the system works in six months or so, when BART police are required to report on the program's initial results.

Updated Jan. 1, 2018, with BART statement that proof of payment inspections would begin in mid-January.