The Utah Transit Authority’s bus Route F401 in Grantsville attracts a minuscule 0.1 rider per mile, agency data show.

Only 4 percent of available seats are filled, even on a small shuttle bus. In fact, the route averaged just three riders per weekday over the past year, data show.

F401 costs an estimated $29.50 per rider trip, making it the most expensive in the system.

This route’s issues of low use and high cost encapsulate some of the tangled questions that UTA faces as it tries to expand its reach and ridership, give all taxpayers paying into the system some service, and hold down costs.

So why does UTA keep F401 running?

The transit agency asked the same question, but ultimately determined it was best to maintain limited service connecting Grantsville to buses serving Salt Lake City and Tooele.

“It had really low ridership. So we thought, ‘This isn’t making a lot of sense,’ so we explored eliminating it,” Laura Hanson, UTA direct of planning, said.

“The community was very vocal in saying, ‘We really need this here,’” and the 10,500 town residents wanted at least some service for the transit sales taxes they pay.

The low rider numbers for Route F401 now are actually an improvement over the past, says Hanson, since UTA switched from more expensive hourly service all day with a full-size bus to two trips in the morning and two in the afternoon on a smaller shuttle. But the limited service makes it more difficult to attract more riders.

Tough choices

The F401 illustrates wider issues that UTA is starting to grapple with systemwide.

UTA President and CEO Jerry Benson recently warned the UTA board that as the agency seeks more riders — including by adding service that is more frequent, later at night, on weekends or to places now not served well — new routes may be similarly inefficient and more expensive per rider, at least at first.

“We need to keep in mind that adding a trip at 8 p.m. is going to be less productive than a trip at 5 p.m. It just is,” he said. “If we’re only evaluating it in terms of how many passengers per hour, you would probably get more putting another one at 5 p.m.”

However, many residents tell UTA they avoid taking transit because service doesn’t run early or late enough to get them to and from jobs or entertainment. These limits are seen as among reasons why ridership remained flat in recent years. So the agency seeks to add service to attract passengers — even if it appears inefficient at first.

Benson said boosted service may lead to a “network effect” to spur growth eventually. UTA saw that in Weber County, he said, when voter-approved tax increases paid for expanded transit.

“As we increase frequency from 30 minutes to 15 minutes on one route, the ridership on two other routes increases because now the connections were there. So at some point you get some synergy and some network effects,” he said.

“But if we just take one route and add service in the evening, we’re not going to see a big part of that [network effect] until you round out the whole system,” Benson said, adding UTA is far from being able to afford that.

When the recession hit, UTA sought to save money by cutting many late or early routes that had low ridership. “So our efforts in those counties that passed Prop 1 is to fill that back out now.”

Proposition 1 to increase sales taxes for transit and roads passed in Weber, Davis and Tooele counties in 2015. But voters rejected it in Salt Lake, Utah and Box Elder counties.

UTA faces a quandary in areas that voted down Prop 1. Waiting for more ridership before adding new service won’t help increase passengers. But adding lightly used routes that may attract extra riders may be too costly.

So Hanson said UTA is constantly reviewing its offerings, trying to achieve the best mix of service in the right places at the right times to serve as many passengers as possible with the money it has — and provide fairness for the taxes residents pay.

Still, some routes are highly used and have low cost per rider, and some are expensive and little used.

Here’s a look at both ends of the spectrum:

Lowest cost per rider

The top 10 UTA routes for lowest cost per rider show an unusual mix.

Four are train lines designed to carry large crowds for long distances with limited stops, what UTA calls “core routes.” The others are mostly special-destination bus routes — sometimes running only a couple of times a day — targeting schools or industrial sites.

The routes with the worst cost per rider often exist to give taxpayers in remote areas some service for their money — such as the F401 in Grantsville. Others are small neighborhood and local routes designed to connect to big core routes.

Others include: Route F546 Draper Flex, $11.81; Route F504 South Jordan Flex, $11.17; Route 677 Layton/Snowbasin ski service, $9.36; F518 Riverton Flex, $9.35; and F534 Herriman Flex Shuttle, $9.29 per ride.

“We recognize some are not performing as well as we would like,” Hanson said, “We dig into the data and say, ’Why is that? Does it have the wrong frequency? Is it in the wrong place? Is it the wrong hours? Was there a corporate pass program that dropped off and the ridership dropped off?’”

UTA tweaks schedules three times a year to try to fix such problems.

Best/worst at filling seats

It is far easier to find a seat on some routes than others, the data show.

Routes that fill the highest percentage of seats include: Route 606 in Weber County to Enable Industries, 74 percent; Route 920 Rose Park (to West High School), 67 percent; Route 919 Fairpark (to West High), 63 percent; and Route 901 from Park City to Salt Lake City, 55 percent.

Others include: Route 608 to Snowbird and Alta, 54 percent; Route 608 in Weber County to DTSI, 44 percent; Route 451 Tooele-Salt Lake City Express, 40 percent; Route 472, Ogden-Salt Lake City express, 40 percent; Route 675 Snowbasin, 38 percent; and Route 526 on 12600 South, 35 percent.

All of the top 10 were bus routes. None was a train line, which may carry more people overall but also has more cars and space to fill.

When UTA sees routes using such high capacity, “Those may be places where we expand the hours of service or the frequency,” Hanson said. “We go through a really detailed analysis for every one of those decisions.”

Average seat utilization on transit across the nation is about 20 percent to 25 percent, she said, about the same as private cars.

The routes that use the least available capacity include: Route 840 UVU Campus Shuttle, 1 percent; F402 Tooele City Circulator, 3 percent; F401 Grantsville shuttle, 4 percent; F400 Tooele Flex, 4 percent; Route 616 North Weber FrontRunner Shuttle, 5 percent; and Route 833 Provo Station to airport, 5 percent.

Others include: Route 645 Monroe Boulevard in Ogden, 6 percent; Route F522, 2200 West Flex Shuttle in Salt Lake City, 6 percent; Route 665 Layton Station to Hill Air Force Base, 6 percent; and Route 628, the recently created Midtown Trolley in Davis County, 6 percent.

Most/fewest riders per mile

Not surprisingly, rail lines generally rank high for the number of riders they have per mile.

Atop UTA’s list is the Blue Line TRAX at 7.9 riders per mile.

Others on the list are: Route 920 Rose Park (to West High), 7.6; Route 919 Fairpark (to West High), 7.0; Green Line TRAX, 7.0; S-Line, 6.6; Red Line, 6.5; Route 608 in Weber County to DTSI, 5.3; Route 606 to Enable Industries in Weber County, 5.1; Route 641 from Orem Station to UVU, 4.2; and Route 2 to the University of Utah, 3.8.

Trent Nelson | The Salt Lake Tribune Riders on TRAX in Salt Lake City, Wednesday March 22, 2017.

The routes with the fewest riders per mile are far lower.

They include: Route F401 in Grantsville, 0.1 riders per mile; F402 Tooele City Circulator, 0.1; Route 616 North Weber FrontRunner Shuttle, 0.2; Route F400 Tooele Flex, 0.2 F546 Draper Flex, 0.2; F504 South Jordan Flex, 0.2; F534, Herriman Flex, 0.3; F518 Riverton Flex, 0.3; Route 664, Layton Station to Hill Air Force Base, 0.3; and Route 880, Sundance ski resort, 0.3.