TWO NEW EFFORTS, one national and the other local, are underway to encourage more people to ride to work on mass transit. Both involve an ingredient that commuters as well as employers have been known to appreciate: money. One is a tax credit proposal in Congress and the other is a discount-fare program just adopted by Arlington County for its employees. Together with other private-enterprise programs that pay part or all of employees' transit fares, these proposals are constructive attempts to get businesses and governments to assist gasoline conservation, use of mass transit and air pollution abatement.

The national proposal comes from Rep. Richard Gephardt (D.-Mo.), who is preparing legislation that would provide tax credits to employers who provide free mass-transit passes to their employees. The bill would further assist employees by exempting the transit aid from any fringe-benefit taxation. For some commuters who would be using subways for long distances, this could amount to a sizable benefit. With local subway and bus fares what they are, Mr. Gephardt may need the Jolly Green Giant's computer system to figure out the possible benefits -- but why not try the plan?

In Arlington, the county government is offering all its employees 20 percent discounts on transit passes. Once an employee signs up, he receives a pass good for a two-week period. The county buys the pass at the regular price, then deducts 80 percent of this cost from the employee's paycheck. Since about 800 of the county's 2,000 employees work at the Arlington County Courthouse -- one block from the just-opened subway station -- the plan should have takers.

For that matter, it should be adopted by other jurisdictions around the region. If the idea does spread, along with the tax-credit proposal, many people who do not live near convenient, dependable and swift public transportation service are likely to complain of unfair treatment. But if their complaints turn into more pressures for better service, the whole region will benefit all the more.