Proposed increase in gas tax likely won't lead to less driving

A proposal to increase the state gas tax by 12 cents to fund billions of dollars in road repairs is making its way through the California legislature this week. While consumers may complain about the higher cost, the increase likely won't convince them to drive less.

Low gas prices in recent years have led to more driving, increased traffic fatalities and a dip in transit use across the country. The current proposed increase in the gas tax isn't likely to change that, said Marlon Boarnet, chair of the department of urban planning at the University of Southern California.

Boarnet co-authored a study on how fluctuations in the price of gas affect driving behavior. He found for every gas price increase of 10 percent, the amount of driving, or vehicle miles traveled, dropped by about 1 percent.

So an increase of 12 cents per gallon equals about a 4 percent increase in the local price of gas. Therefore he would expect to see about a 0.4 percent decrease in driving.

"That increase by itself will not have much of an effect in reducing driving immediately," he said, noting it's common to see increases bigger than 12 cents a gallon on a weekly basis based on market forces.

But longer-term trends could amplify the effect. 

The current proposal would tie the tax rate to inflation, so it would inevitably rise in coming years. Until now, the gas tax has remained at its 1994 per gallon rate, despite increases in other costs.

The state Legislative Analyst’s Office predicts the price of gas in California could increase by between 26 and 75 cents a gallon in the next 15 years because of fees charged to energy companies through the state's cap and trade market, which seeks to offset carbon emissions by charging polluters and putting the money toward projects which reduce greenhouse gases.

That program is set to expire in 2020 unless two-thirds of the legislature vote to extend it.

As to whether bigger changes at the pump might add up to bigger ridership on buses and light rail, the Los Angeles Metropolitan Transportation Authority's own research shows gas prices have minimal effect.

While Metro saw spikes in ridership during previous gas price increases, like the massive one in 2008, L.A. ridership is generally less sensitive to changes in gas prices because about 70 percent of daily riders don't have access to a car in the first place.

Boarnet said in general all drivers have been becoming less sensitive to increases in gas prices over time as incomes have risen and transportation costs make up a decreasing share of our budgets.