An elevated commuter rail system that runs past Pearl Harbor and Honolulu International Airport would cost more to build and maintain, but carry more passengers and alleviate more traffic.

Those are among the findings in the city's draft environmental impact statement, which analyzes the effects of both routes. The recently released study is a key resource as the Honolulu City Council debates switching the route of the planned train from Salt Lake to the airport.

The current Salt Lake route was set in March 2007 in a political compromise between rail proponents and City Councilman Romy Cachola, who supported rail only if it went through Salt Lake. A change in political dynamics following the general election vote in support of rail, however, has increased pressure to switch the route to the airport.

Despite the political nature of the city's decision-making process, there are legitimate reasons for the city to pursue either route, said Peter Flachsbart, an associate professor of urban and regional planning at the University of Hawai'i-Manoa.

"It is very much a political decision — the routing — (but) if you open it up to more rational reasons, you can point out the pros and cons of either one," said Flachsbart, who favors a Salt Lake route.

Each alternative has advantages and disadvantages, according to the project's draft environmental study. While the Salt Lake route was chosen mainly because of a political compromise, it does serve more residences than an airport route. An airport route, however, would serve more employers.

Despite the different characteristics of Salt Lake and the airport district, there aren't major differences in the benefits and environmental impacts of either route.

COST DIFFERENCE: $220M

The biggest advantage of a Salt Lake route is cost. The slightly shorter route is projected to cost $4.28 billion to build, which is about $220 million less than the airport route's $4.50 billion price tag. That cheaper route is the only alternative that's affordable within the city's current financial plan, according to the city's draft environmental impact statement.

The city plans to start work on the rail line in late 2009. Limited service between West Loch and Waipahu would start in late 2013, and full service to Ala Moana would begin by the end of 2018.

Proponents of a Salt Lake route contend the train should serve a predominately residential area, which could help drive up ridership. Airport route proponents argue that the costlier route is more convenient for the broader Honolulu community, which also could generate higher ridership. Higher ridership means the system will require less in subsidies to pay for operations and maintenance.

"It's still our belief that the best route, if rail does go through, is the airport route," said Brennon Morioka, director of the state Department of Transportation.

"It drives up your ridership and it makes sense for future growth as well when you start talking about spurs to UH and Waikiki. Just having it go through the airport makes more sense."

OVERESTIMATING USAGE

Because it would serve more employers, the airport route is expected to attract more riders. The city's draft environmental impact study predicts there will be 95,310 daily train riders on the airport route in 2030, which would be nearly 9 percent higher than a Salt Lake route. That would lead to a 23 percent reduction in daily vehicles hours of delay on Honolulu roads, which is slightly more traffic relief than predicted for a Salt Lake route.

Those projections would favor building an airport route. However, train ridership projections generally tend to be inaccurate and typically overestimate actual ridership.

According to an April report by the Federal Transit Administration, recently opened federally subsidized train projects are expected to carry, on average, just 74.5 percent of their originally forecast ridership.

Salt Lake resident and former area Neighborhood Board member Mike Taylor said the city's higher ridership forecast for the airport route doesn't make sense. That's because Salt Lake's higher residential population results in a higher potential ridership base. In addition, there is no timetable or financial plan for extending the train into tourist-popular Waikiki.

"I think that any person out there that looks at this issue dispassionately would instantly and immediately think the airport is a logical alternative," he said. "That's just thinking about it for five or 10 minutes. The first priority is to service commuters who are going to ride the train into town," Taylor said.

"That's how you maximize your ridership. Airport travelers with luggage are not going to be a real strong draw to ride the train. It's not convenient for them."

By skipping the airport and Pearl Harbor, the Salt Lake route would provide the most direct connection between East Kapolei and Ala Moana. An end-to-end trip on the airport route would take 42 minutes, or about 2 minutes longer. The shorter Salt Lake route is expected to generate a slight increase in through trips, but substantially fewer trips to Pearl Harbor Naval Base and the airport.

BENEFITS TO EMPLOYERS

In addition to improving airport access, the airport route would provide better access to major employers such as Pearl Harbor and Hickam Air Force Base. That could spur the federal government to provide additional money to offset the route's higher costs, said City Council member Charles Djou, who supports an airport route.

"I think by connecting the airport and Pearl Harbor you make a better case for federal funding," he said.

High gasoline prices coupled with newer, faster train systems are expected to result in a slight increase in the popularity of public transit once rail is built. However, it's unclear whether the train will spur workers at Pearl Harbor and in the airport area to leave their autos at home.

"The fact is that the parking at Pearl Harbor and Hickam is so plentiful," said Tom Strout, a Salt Lake Neighborhood Board member. "Why would the people give up their cars? I can see that the airport route would get used. I just don't believe it would be used as heavily" as the Salt Lake route, Strout said.

Beyond ridership and cost, the two routes have mixed impacts on the environment including land use, noise pollution and on archaeological resources.

Both routes will displace businesses and homeowners. However, the airport alternative would require about 6 percent fewer parcel acquisitions than the Salt Lake alternative. Overall, 193 properties will need to be fully or partially acquired to build the Salt Lake route, versus 182 properties on the airport route. Both routes would displace 20 homes.

Although it would affect fewer properties, the airport route would have more of an effect on historic and public park resources. The airport route would use a small, half-acre portion of the Pearl Harbor National Historic Landmark. The airport route also would have a larger effect on public park land at Ke'ehi Lagoon Beach Park. The guideway would pass 40 feet above 2.8 acres of the 72-acre park's mauka side.

CAN SALT LAKE MOBILIZE?

Among other effects, the fixed guideway would have a greater visual presence and generate more noise along Salt Lake Boulevard, but require the removal of significantly fewer street trees than an airport route.

Archaeological resources and burials are expected to be an issue with either alternative. However, the likelihood of encountering burials is slightly greater for the Salt Lake alternative than for the airport alternative.

The airport route also would result in slightly less air pollution and energy consumption, according to the city's draft environmental impact study.

Because of its lower costs, the Salt Lake route is slightly more cost-effective. However, either route would be cost-effective enough to qualify for federal funds, according to the draft environmental impact study created by New York consultant Parsons Brinckerhoff.

Just which route the city decides to take depends in part on how well Salt Lake and other communities can mobilize support on their behalf. The route also hinges on whether the city can secure more money to cover the airport route's higher cost.