THIS WEEK again saw the implementation of Spare the Air days, during which many mass transit agencies offer free rides as a way to alleviate air pollution and traffic congestion.

And surprise, public transit agencies saw a spike in ridership, which was hailed as a success. Of course that spike went away the next day when the free rides disappeared

Sure, it might have had some impact in regards to taking vehicles off the road to fractionally help with air pollution that mounts on these very hot summer days.

But this second round of three Spare the Air day costs taxpayers $5.3 million, on top of the $7.5 million spent in the Bay Area for the previous three days last month.

We would argue that the more than $12 million spent on this promotional campaign would be better used to help alleviate gridlock on Interstate 580, which is quickly moving up among the most-congested commutes in the Bay Area.

Earlier this year, plans were finalized for an eastbound high occupancy vehicle lanes, or HOV lanes, for I-580 from Hacienda Drive in Pleasanton to Greenville Road in Livermore. While the funding mixture of local, state and federal money is still coming together for the $55 million project, the $12 million spent on Spare the Air days could have funded more than 20 percent of the project.

Or better yet, that $12 million could have gone toward funding a westbound HOV lane that has yet to hit the drawing boards due to a lack of funding. Or it could go to building a better transition from I-580 to Route 84.

In the business world devoid of taxpayer money that always seems to be there for public officials, return on investment is the real gauge of success.

We have seen very little if any return on the investment of $12 million to give free public transit in the Bay Area.

Ridership spikes evaporate the next day fares are collected and the impact on air pollution is fractional at its very best. The idea of introducing public transit to those who would not normally use it in hopes of converting a driver into a rider has not materialized in any quantified manner.

The extra Spare the Air days are being paid from a windfall of tax money that has made its way to agencies such as the Metropolitan Transportation Committee. The state is seeing a spike of its own as tax revenues are outpacing expectations.

We would feel a whole lot better if this money was being used for tangible transportation remedies rather than a feel-good PR campaign.