Cal Poly on 91-Exprs

The Fed Highways sponsored study of 91-Express Lanes in its "interim findings" report suggests the project is attracting its toll paying traffic from a variety of corridors not just from the free lanes alongside. And latent demand may be asserting itself, now that congestion is reduced. The study is by Edward Sullivan, engineer at Cal Poly Univ San Luis Obispo and consists of collecting before and after traffic data and surveying motorists to test various hypotheses about the congestion pricing express lanes project that consists of 4-lanes divided of HOV-3 free/others tolled, built by investors in 14km of the median of an 8-lane freeway in northeast Orange Co Calif. The shift of traffic out of the adjacent 8 free lanes is surprisingly small Sullivan notes, though there has been a marked improvement in traffic flow and a major reduction in congestion. Peak congestion upstream of the Exprs Lanes may be imposing a metering effect at the height of the peak producing a 'sag shape' rather than the more typical 'hill' in the time series, he writes.

Sullivan finds no change in overall vehicle occupancy after the opening of 91-Express. He told us there may be offsetting forces at work. At the same time 91-Exprs was opening and making travel easier for HOV, government authorities were abandoning legal pressure on employers to promote car-pooling of employees, and a parallel commuter rail service was opening — so 91-Exprs may have helped prevent a drop-off in vehicle occupancy.

Cal Poly opinion surveys show support for the Express Lanes — 65% among toll payers, 62% among free-HOVers sharing the Exprs Lanes, 53% among free lanes drivers. Among those opposed to tolling about equal proportions equate tolls with increased taxes or think the differential service is "unfair" though a lot of other criticisms are expressed. Sullivan says support for toll express lanes is growing : "This clearly seems to be a case of familiarity generating acceptance." (Contact E. Sullivan 805 756 1166 esullivan@airship.calpoly.edu)