The Truth About Existing and Proposed Ferry Transit for San Francisco Bay

BY JIM SWEENEY

Last July, when expanded ferry service was being proposed by the Bay Area Council, Russell Long, Executive Director of Bluewater Network, issued the "Bay Area Transit Options Emission Report" on the internet. This Report raises speculative concerns that are backed up by an impressive array of data tables, bar graphs, footnotes, and references. Its stated intent was to enable unbiased quantitative comparisons of the harmful engine emissions per passenger mile of commuter automobiles, transit buses, and a modern fast ferry operating between Larkspur and San Francisco. It concluded that, with the 1999 mix of transit alternatives, the ferry generates 6.7 times the emissions per passenger mile of the automobiles and about 13 times that of the buses. Projecting engine progress to the year 2010, the Report concluded that the diesel ferry would by that time be even worse, with 8.8 times the emissions per passenger mile of an auto, and about 20 times that of a bus.

These findings were, to say the least, astonishing. As frequently happens with sensational news they were repeated in the national press, by Dr. Long himself in public appearances and on television, and echoed in statements by government administrators and politicians. Capitalizing on the new "buzz" Bluewater Network issued another report from its website stating that modern fast ferries are inherently unsafe. All this has contributed significantly to Dr. Long’s notoriety as an outspoken critic of waterborne public transit and commerce.

I am a native San Franciscan and lifelong Bay Area resident who has commuted around the Bay Area, primarily by public transit for the better part of forty years. I belong to the Sierra Club, endorse and support all its environmental protection goals, and am employed by an engineering firm that has accomplished engine exhaust emission comparisons in support of California State Air Resources Board and South Coast Air Quality Management District programs.

I have examined Dr. Long’s Reports and determined that, while they were hopefully prepared with good intentions, they do not withstand scrutiny. The truth of the matter is that the sensational conclusions reached by Bluewater Network not only defy the laws of physics but also fly in the face of U.S. marine safety and environmental regulations, procedures, education, and tradition. They have no basis in reality and are, in a nutshell, dead wrong.

The exhaust emissions of present ferry diesel engines per passenger mile are in fact comparable to those of competing land transit vehicles. Projecting into the future, engineering developments are bound to benefit all transit modes (probably more for ferries than land vehicles).

So, gentle reader, by now you must be wondering, " How could Bluewater Network possibly reach such far-out conclusions?" Let’s take a closer look at Dr. Long’s Bay Area Transit Options Emissions Report. The essential point to bear in mind is that this was supposed to be a quantitative analysis. In other words, regardless of the methodology selected, his analysis must either succeed or fail based upon the validity of the numbers assumed. Bluewater Network’s transit emissions analysis exhibits a remarkable proclivity to "compare apples to oranges". It then compounds the errors of individual (apple and orange) factors by multiplying and dividing them to arrive at the wildly unrealistic numbers used for its comparisons, namely: (1) grams of harmful engine exhaust emissions (2) per commuter moved and (3) per mile of commute trip.

Specifically:

COMMUTER (PASSENGER) COUNTS

Dr. Long selected a baseline of 1.15 people per trip as the average Bay Area commute automobile ridership. This is a valid assumption and I have no quarrel with him on that point.

For transit buses, he selected 35 passengers per trip. This is the average Bay Area peak commute hour bus patronage, a statistic that allows for the number of empty seats during a typical bus trip (from beginning to end) but does not take into account either empty (deadhead) bus operations between the central dispatching yard and the start and stop of revenue service on various routes, or patronage during off-peak hours. Buses obviously generate exhaust emissions during all these non-commute hours of the day.

For the ferry, he chose the average number of passengers moved per commute hour round trip (157.4) a statistic that includes the very low patronage figures on reverse commute voyages. The Bluewater ferry patronage assumption, while 4-1/2 times that of one bus, is therefore only about half what it should be for comparison purposes to the buses.

If one were interested in making a fair ridership comparison, there could be two ways of doing it. Either rate both the bus and ferry on peak ridership numbers, during commute hours, or rate both on an all-day basis.

If peak commute hours are chosen, the bus would be moving an average 35 passengers per trip and the ferry would be moving an average 320 passengers per trip, which is over nine times that of the bus.

If total daily service is being considered (a much better yardstick for evaluating the overall impact of engine emissions on air quality) then the bus figure would be reduced to between 11.8 and 18.2 average passengers per trip (the actual all-day average transit bus patronage) and the ferry figure would be similarly reduced to an average of between 129 passengers per trip. If we take the midpoint of 15 passengers per average bus trip and 129 passengers per average ferry trip, the ferry is still demonstrably moving 8.6 times as many passengers per day as the average transit bus.

Using its skewed assumptions, the Bluewater Report concluded that either 5 buses or 135 automobiles can transport the same number of passengers as one ferry, when in fact 9 buses and 278 automobiles are needed. From an emissions standpoint, to say nothing of street congestion and inner city parking, the much larger numbers of vehicles taken off the road for displaced by one ferry are highly significant.

ENGINE EXHAUST EMISSIONS

The Bluewater Report uses fleet average engine emissions data (hot running) for the automotive fleet. This overlooks several important factors:

1. It does not take into account the fact that roughly a third of the personal vehicles used by Marin County commuters in 1999 were not high mileage automobiles, but "gas guzzling" pickups and SUV’s.

2. It ignores the 40% higher emissions produced during "cold start" conditions which occur at least twice per day for each personal commute vehicle.

3. Fleet average emissions data are based upon steady state engine load tests and do not reflect the actual load profile of a personal vehicle commute. The real trip involves both long flat stretches and steep grades north of the Golden Gate Bridge, plus hills in the city of San Francisco. More significantly, dozens of vehicular stops, accelerations, and decelerations are required due to daily street and highway congestion, bridge toll, street maintenance, construction projects, traffic signals controlling intersections, and accidents. (The glaring proof of this is that the average speed of an auto making the trip is less than 27 miles per hour on a "good" day. On a "bad" day, the situation can be much worse.) From an engine standpoint, all these load transients and delays boost vehicular emissions per mile far in excess of what would be predicted by steady load fleet average emissions tests. After all, a stopped car produces an infinite number of emissions per mile because it is not making any miles of headway.

While the exact impact of these combined factors is unknown, engine technology and common sense definitely establish that their vectors all point in the direction of higher automotive emissions per mile, probably in the order of at least 60% in excess of the fleet average emission data assumed for the Bluewater Report.

For its bus comparison figures, the Bluewater Report used dynamometer test numbers. Again, these tests represent a "pristine" kind of data not reflective of real commute conditions. Buses are subject to even more delays and stops than automobiles, as buses must pick up and discharge passengers in addition to suffering the same traffic impediments as automobiles. Transit buses average only about 24 miles per hour between Larkspur and downtown San Francisco (on a "good" day). Anyone who has seen the rear of a bus as it accelerates away from a curb or starts to climb a steep hill is aware of the black cloud of exhaust fumes created at such times. These emissions, created at unavoidably repetitious intervals, are completely ignored by Bluewater’s choice of dynamometer test data. Actual bus emissions per passenger mile are probably at least about 65 to 70% greater than dynamometer test results.

In all fairness to Dr. Long, actual automotive and bus commute emissions are very difficult to assess without substantiating field tests that remain to be conducted. Automotive fleet average emissions and dynamometer tests are about all that have been published and all that could be obtained from academic or government air quality data sources. However, such statistics, while valid for baseline comparisons to comparably derived test results, have about as much bearing on actual commute emissions as the numerically correct, but equally irrelevant top speed of James Bond’s BMW.

At my recommendation, the U.S. Department of Transportation is presently developing a program to establish valid statistics on actual commute vehicle exhaust emissions.

For assessing ferry emissions, the Bluewater Report selected and described M/V DEL NORTE, the newest and fastest ferry on the Bay and the star of the Golden Gate Larkspur ferry fleet. However, Bluewater did not use data from the DEL NORTE’s modern, low emissions (electronic injection control) Detroit Diesel engines for emissions comparisons. Instead, the Bluewater Report improperly assumed emissions data from a much older East Coast (Long Island, NY) ferry’s Caterpillar engine with outdated mechanical injection control. This is invalid assumption negates all diesel engine emissions progress (roughly a 50% reduction per unit of power generated) over the past ten years.

Further, I think it is important to note that the DEL NORTE engines are kept warmed up all day, and therefore experience no more than one cold start per day. Even more significantly, the ferry schedule, being free of highway and street traffic congestion, grades, and other routine rubber-tired vehicle delays, is the only one of the three modes being compared with a flat load profile. Ferry engines are therefore able to achieve minimum exhaust emissions not physically possible for automobiles and buses.

TRIP MILES

For mileage, the Bluewater Report assumed that the distances travelled by commute auto, bus, and ferry are all equal, ignoring the fact that the ferry’s direct water route is about 20% shorter than the competing land and bridge route.

CARBON MONOXIDE

Last, but not least, the Bluewater Report’s choice of emission components ignores carbon monoxide, the chief pollutant of automotive engines, a poison gas, and a major contributor to the global warming "greenhouse effect". This oversight unjustly benefits automobiles when compared to the diesel powered buses and ferries. Diesel engines produce very little carbon monoxide.

Space does not permit me to continue, but the foregoing points should be sufficient to convey the general idea. Practically every assumption used in the Bluewater Report is severely biased against ferry transit, with a cumulatively negative impact on credibility.

I would like to make a couple of additional comments to put the whole ferry debate back into perspective.

First, assume a fleet of seventy ferries serving a comprehensive regional ferry network becomes an operational reality. The total impact of this fleet on Bay Area air quality, compared to the millions of automotive vehicles, stationary industrial operations (power generating facilities, oil refineries, etc.) will be comparable to that of a box of matches in a forest fire.

There is no question but that environmentally friendly ferry vessels can be built. And there are compelling reasons why they should be built soon. The over-riding imperative for water transit is the projected 250% population increase in the Bay Area by 2020. The cost (in public funds, land use, and quality of life) of additional land transit infrastructure in our seismically hazardous State of California is prohibitive.

For a comprehensive discussion of ferry social, environmental, and economic considerations, including operational safety, I recommend you obtain a copy of the report "Ferry Transit Systems for the Twenty First Century", dated Jan.10, 2000. This document was prepared by an ad hoc panel that I volunteered to chair on behalf of the Society of Naval Architects and Marine Engineers. Copies are available from the Society headquarters, 601 Pavonia Avenue, Jersey City, NJ 07306, or by accessing the Society website: http://www.sname.org.