Diamonds Aren’t Forever
November 20, 1998
On a December morning last year, a patch of pea soup fog caused a horrific pile-up on Interstate 5, closing all lanes into Sacramento at the beginning of the rush hour commute. The Highway Patrol immediately detoured the blocked traffic onto a parallel freeway, Route 99. And the first thing they did on Route 99 was to open the diamond lane to all traffic.
Why? “To increase the capacity, of course,” said one CHP official, who sounded somewhat incredulous at the question.
A more important question is, why is something so obvious to a CHP officer managing a traffic crisis utterly lost on the bureaucrats at CalTrans? California’s highway officials plan to double the number of diamond lanes clogging California freeways by 2015.
Meanwhile in New Jersey, transportation officials have come to an entirely different conclusion. On November 30th, they abolished the diamond lane restrictions along two heavily traveled routes. The relief was immediate. One commuter accustomed to diamond lane gridlock marveled, “this morning, it was zooming. Everybody was going along like a normal highway.”
This shouldn’t surprise anyone. A typical diamond lane carries only 7 percent of the traffic, yet it consumes 25 percent of the capacity on a four-lane freeway. This means the remaining 93 percent of the traffic is deliberately crammed into 75 percent of the space.
CalTrans officials insist that diamond lanes encourage carpooling based on the false assumption that every car with more than one person is a carpool specifically created to take advantage of the lane. The engineering studies on diamond lanes, including one from U.C. Berkeley’s Institute for Traffic studies, are quite clear that the formation of new car pools is negligible and doesn’t begin to justify the deliberate gridlocking of the highway system. A study of the Route 55 Freeway in Costa Mesa concluded that the diamond lane costs commuters the equivalent of 11,000 passenger trips per day.
A quarter century of experience backs up these studies. The percentage of passengers who use diamond lanes has remained stable for many years, despite the proliferation of diamond lanes throughout California.
Nor are diamond lanes any help to the environment. Diamond lanes deliberately create gridlock, and gridlocked traffic produces twice the NOX contaminants and six times the carbon contaminants per mile than produced by traffic operating at peak efficiency. Diamond lanes have, in fact, been an environmental disaster for California.
Diamond lanes even defy their own logic. The diamond lane is supposed to give commuters an incentive to carpool, by offering the vacant diamond lane as an alternative to the artificially congested lanes. But as commuters do so, the diamond lane congests, the other lanes decongest, and the incentive disappears. Even if they worked, they couldn’t work.
In reality, diamond lanes simply provide the illusion of relief to the small percentage of traffic that can use them, while artificially gridlocking the 93 percent of the traffic that cannot.
The most common defense is that new lanes will quickly fill up with traffic and congestion will end up being as bad as it was before. In other words, California’s top transportation officials argue, “Don’t built more traffic lanes; people will use them.” Our modern bureaucrats prefer to build transportation systems that people don’t use.
It is a natural condition of human nature that the more we invest in our mistakes, the less we are willing to admit them.
Several years ago, a CalTrans official in a rare moment of candor explained the real purpose of the diamond lane. He said it was his job “to make life miserable for the single motorist.”
They have succeeded. Diamond lanes now clog virtually every major freeway artery in California. But diamonds don’t have to be forever, as New Jersey has proven.