HOV lanes cause huge solo driver increase on Montague Expressway

Traffic engineers' continue disinformation on HOVs

Akos Szoboszlay, P.E., President, Modern Transit Society
Oct. 24, 1992
Update in July 1998

The traffic engineers of the Santa Clara County Transportation Agency (SCCTA) continue their practice of disinformation regarding the results of HOV [High Occupancy Vehicle] lanes, also called "carpool lanes." In the County's general plan for transportation, titled T2010 (amended in 1991), page 54, it states that "Overall, ridesharing increased approximately 25% on these Commuter Lane projects." Yet, nowhere in the entire report did SCCTA give the solo driver increase as a result of constructing the HOV lanes.

The fact is, many more solo drivers were added to the roadway during commute hours as a result of constructing the HOV lanes. For example, on Montague Expressway during commute hours in the peak direction, there are 4562 more daily solo driver commuters vs. 1207 more HOVs, comparing the years 1982-1988. Furthermore, HOV is defined as one passenger in the vehicle, an unusual definition that makes carpooling appear more favorable. Solo drivers account for 79% of these 5769 vehicles added to the road by constructing the HOV lane. [Source: Commuter Lane Performance Evaluation, March 1, 1989, by Santa Clara County Transportation Authority]. Anytime a road is widened from 4 to 6 lanes, you have to expect an increase in all types of vehicles -both solo driver and HOV. Yes, the number of HOVs did increase on this road (while dropping county-wide). But, leaving out the far greater increase in solo drivers misrepresents the increase in HOVs as a switch from solodriving to carpooling. A first-approximation as to what actually happens is that the HOVs move over to the HOV lane upon construction. This creates a reserve capacity [or "vacuum", figuratively speaking] in the other lanes that is taken up by solo drivers.

Similar results were obtained on both San Tomas Expressway and Rt. 237. The increase in solodrivers was between two and three times the increase in HOVs, as a result of constructing the HOV lane. Again, the increase in HOVs is a result of people switching from paralleling routes, not from switching from solodriving to carpooling, as further evidenced in the next paragraph and the update below.

In fact, there has been an incredible loss in both the absolute number of HOVs, and the percent of HOVs (as market share), for the County despite the fact that 115 miles of carpool lanes have been constructed in Santa Clara County during the same period, 1982 to 1990. The absolute number of carpoolers dropped by over 10,000 people per day. The market share of HOVs fell from 17% to 12.5% of commute trips between 1980 and 1990 (even using the unrealistic definition of only one passenger and one driver per vehicle.) [Source: "Demographics, Trends and Air Quality Working Paper" by SCCTA, dated Dec. 1990, page 37.] In the meantime, both the market share of solodriving and the absolute number of solo drivers has increased. By any kind of business analysis, if an investment is made to increase market share, and by spending the money for the investment, the market share decreases, the investment is unquestionably a colossal failure.

Yet, the SCCTA traffic engineers sent out a press release stating that HOV lane construction was "a great success" in 1985, and they continue to misrepresent HOV lanes as a success by selectively ignoring relevant data in the T2010 report. The purpose is to exert political pressure for more road construction (their livelihood).

Furthermore, MTS questions the definition of HOV as one passenger in an automobile. From a Rt. 237 questionnaire [report dated March 1, 1989], 51% of carpoolers commute with a family member. How many of these make two round-trips a day, by driving a spouse to work, thus doubling the air pollution and increasing congestion compared with solodriving? This round-trip type of HOV is worse than a solo driver for both pollution and congestion.

The T2010 report statement "Commuter Lanes ... reduce air pollution and energy use" [page 51] is false because the term "Commuter Lane" is used as a euphemism for road construction to increase automobile capacity. HOV lane construction is a solo driver incentive in disguise, and therefore increases air pollution. County data show that HOV lane construction increases solodriving much more than carpooling. These commuter lanes increase air pollution. It should be obvious that for the example of Montague Expressway, the addition of 5769 vehicles a day will not "reduce air pollution" as is claimed by the county traffic engineers who authored the T2010 Plan.

In sharp contrast to HOV lane construction, designating existing lanes as HOV will decrease air pollution. This major difference has been whitewashed by the county traffic engineers and the T2010 Plan.

Update, July 1998

The following information was in the news [for more info, contact the source, RIDES]:

Cars hauling only the driver are appearing more and more during commute hours on San Francisco Bay area highways. That's the conclusion made in a study by the group RIDES for Bay Area Commuters. The study found 71% of commuters drive alone to their jobs. The figure was 64% in 1996.

HOV lanes are not a "great success" as claimed by traffic engineers, if success is a reduction of solodrivers. They are only a success when the goal is to build more highway lanes. The Clean Air Act prohibits increasing highway capacity in smoggy regions. But HOV lanes have been given an exception under the false pretense that they decrease solodriving and decrease pollution.

Index of articles on HOV (carpool) lanes

Details for those studying HOV lanes:

All vehicle counts are when HOV lanes are activated, AM+PM commute.

Montague Expressway has no nearby paralleling roads as a result of perpendicular Freeway 880 and two rivers, plus San Jose Airport to the southwest. The nearest paralleling road is Rt. 237 (freeway) which already had HOV lanes, and even this is about two miles distant. This explains why the percent of solodrivers added to the road as a result of HOV lane construction on Montague Expressway (79%) was higher than for San Tomas Expressway (73%) and for Rt. 237 (63%): carpoolers of paralleling routes did not shift to Montague as a result of constructing the lane.

Akos Szoboszlay, MTS President, and an engineer by profession, analyzed vehicle counts and wrote detailed reports giving much more detail than contained in this web site. This, or even original vehicle counts, are available upon request on paper or FAX. The vehicle counts are from Santa Clara County Transportation Agency (now re-organized as Santa Clara County Roads and Airports).

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