A new study says light rail lines to airports may be popular politically, but they don’t make sense economically. Exhibit A: The Utah Transit Authority’s Green Line TRAX to the Salt Lake City International Airport.

“The extension receives middling ridership, even by the standards of a light rail system with generally poor performance,” says the study by the Manhattan Institute, a conservative think tank whose mission is to “develop ideas that foster greater economic choice and individual responsibility.”

The TRAX extension from downtown Salt Lake City to the airport cost $350 million when it was completed in 2013. The study says that money could be better spent elsewhere, especially on buses.

Study author Connor Harris looked at 23 light rail systems in the nation to come up with recommendations about where and when such systems make sense, and when they should be avoided. His main conclusion is that bus rapid transit systems — such as the new Utah Valley Express in Provo and Orem — are usually smarter, cheaper, more flexible and work better overall than light rail.

The study highlights what it says are common errors with light rail systems, including “overvaluing certain classes of destinations such as airports.”

Airport lines “tend to perform poorly” because they are remote from population centers, require extensive construction and their routes tend not to serve many people or dense developments along the way, the study said.

Still, “it’s easier to form a broad political coalition for airport service than for run-of-the-mill transit improvements,” it said. “City power brokers like to impress out-of-town visitors with airports, and suburban residents who do not use transit regularly imagine that a train for their occasional airport trips would be convenient.”

Three airport light rail lines are singled out as examples of projects that were expensive but attracted relatively low ridership, in Dallas, Denver and Salt Lake City.

While the airport in Salt Lake City is close to downtown, the 5.5-mile journey includes a 3.3 mile nonstop segment — and it has only mediocre ridership for a big investment.

“The airport station averaged 1,355 daily boardings in 2018, ranking 16th in the system out of 58 total stations. The other four stations on the [airport segment of the] line ranked 25th, 27th, 37th, and 50th with the poorest-performing station receiving only 168 riders on an average day in 2018,” the study said.

UTA spokesman Carl Arky disputed the study’s conclusion.

“The Green Line to the Salt Lake City International Airport is successful and provides a quick connection to downtown Salt Lake City and the rest of the system," Arky said. "Having a rail connection to the airport has provided Salt Lake with benefits in tourism, conventions and businesses wanting to locate along the Wasatch Front.”

The airport extension of TRAX has sometimes been controversial. It was criticized when it opened because it does not begin operation early enough to serve early flights and ends too soon to serve late ones. The problem is worse on weekends.

Also, the city pushed for a $68 million elevated-track extension of the line for just a couple of blocks at the airport to serve its soon-to-be-completed new terminal — but that was trimmed down to an $18.6 million street-level extension instead.

Salt Lake City International Airport Executive Director Bill Wyatt said last year that while most forms of ground transportation service have boomed, an exception seems to be the TRAX line with its relatively low and stagnant ridership. UTA countered that ridership on that line last year had been increasing.

The Manhattan Institute study also criticized some other transit agency practices nationally that UTA has embraced. It pointed to an “overemphasis on serving transit-oriented developments,” or mixed developments of housing, retail and office buildings near train stations.

UTA has used its land to form multiple partnerships with developers for such projects. But state audits have criticized the agency for past sweetheart deals that enriched developers at the expense of taxpayers. The Utah Legislature imposed a cap on the number of these transit-oriented developments for a time but has since lifted that with the restructuring of the agency.

The Manhattan Institute study also said that bus-rapid transit “offers a better, more economically sustainable path forward” than light rail. Bus-rapid transit often provides bus-only lanes, longer buses and ticket purchases before boarding.

UTA is planning several such projects, including a bus-rapid transit route from downtown Ogden to Weber State University, a West Valley City-Taylorsville-Murray line and one through Davis County to downtown Salt Lake City.

At the same time, UTA is considering more TRAX projects, too. It currently is studying a possible $1.2 billion TRAX extension through the site of the current Utah State Prison to Lehi. State officials are pushing that to promote the development of the soon-to-close prison site.

Arky said UTA considers all options when planning for future improvements and expansions of its network.

“UTA and our transportation partners continue to study the right mode of transit to fit the need and the market,” he said.