Measure M is one of the most promising ballot measures to pass in Los Angeles County in recent years.  It offers $120 billion in long-term sales tax revenue to fund transportation projects — the kind of money that can help transform mobility in the region.

But the money brings perils, too, which I describe in a Los Angeles Times op-ed today:

If history is any guide, L.A. transit leaders have a habit of prioritizing politically expedient projects over ones that would benefit more riders. Faced with NIMBY opposition, our leaders too often cave.

Just look at the Expo Line from downtown L.A. to Santa Monica, a route that remains hampered by slow travel times after transit leaders failed to give the train priority over automobiles along city streets. Additionally, failure to push through with adequate development projects along the route denied this expensive rail technology an easy ridership boost.

Will transportation leaders similarly compromise away good Measure M projects until they go bad?

To answer this question, it’s important to understand what a “good” project entails. Cost-effectiveness — using the fewest dollars to move the most people the greatest distance — is key. Projects should attract maximal ridership, based on existing population, job density and service quality. Potential ridership, based on the feasibility of building more housing, retail and offices within walking distance of stations, is another crucial determinant. (The failure of the anti-growth Measure S in the recent L.A. election adds even more weight to this component.) Finally, projects should maximize reductions in overall driving miles, air pollution and greenhouse gas emissions.

The piece details some immediate tests facing Metro leaders and offers recommendations to ensure that they make smart decisions. The long-term future of LA in many ways will be determined by these short-term actions.