Why there are fewer cars now on Salt Lake City’s 400 South

TRAX is driving down traffic volume along this key road connecting downtown to the University of Utah.

(Rick Egan | The Salt Lake Tribune) Traffic on 400 South in Salt Lake City on Tuesday, Jan. 5, 2021.

If you think there is less traffic along 400 South now than there was 20 years ago, you’re right. If you think light rail has nothing to do with that, you’re wrong.

A new study shows TRAX continues to reduce congestion along Salt Lake City’s main corridor tying downtown with the University of Utah — even as both are growing dramatically.

Thanks to the trains, volumes of automobile traffic along heavily traveled 400 South remain well below levels seen before the Utah Transit Authority’s 2001 completion of its Red Line connecting the U. with the city center, and the rail extension opened in 2003 to U.’s medical campus.

In fact, counts of average daily traffic along 400/500 South stayed consistently between a half and two-thirds of their pre-TRAX range for at least a decade after the lines launched, researchers found, even as the numbers of U. students, faculty and staff have grown rapidly and commercial and apartment development along the busy street has exploded.

While 400 South’s average daily traffic counts reached 41,347 in 1999, according to data from the Utah Department of Transportation, those counts fell to 22,692 by 2004 and hovered in that range through 2014. They’ve risen a bit since, but at slower rates than you would expect, given other trends.

The study’s findings are likely to buttress the U.’s ongoing partnership with UTA in future years as a construction boom on campus rolls ahead, while also supporting the U.’s policy of subsidizing TRAX passes for students.

“Light rail along 400 South is a super amazing asset for Salt Lake City,” said study co-author and U. graduate student Brandon Siracuse. “We should be doing everything we can to leverage it to help offset the effects of increasing population.”

(Rick Egan | The Salt Lake Tribune) Traffic on 400 South in Salt Lake City on Tuesday, Jan. 5, 2021.

The study ran traffic comparisons over the same period with 700 East and 1300 East, which run north-south and don’t have rail lines, to solidify findings on the impact on 400 South of TRAX ridership.

Without the resulting reductions in traffic congestion due to light rail, the study concludes, the 400/500 South stretch “would regularly experience gridlock conditions.”

Researchers also documented significant benefits from less traffic in the form of lower fuel consumption and reduced air-polluting emissions into Wasatch Front skies as well as substantial savings on parking and associated costs on campus.

Shift since 2014

The study by the U.’s Metropolitan Research Center also found that after staying relatively flat for the decade after 2004, traffic counts along the corridor crept up beginning in 2014 as TRAX ridership also ticked down.

Average daily traffic along the stretch went from 23,200 in 2014 to 27,599 in 2018, according to transportation data, while ridership numbers slipped by nearly 8% over the same time period.

While walking and biking along 400 South appear to have increased due to light rail, partly explaining ridership declines, Siracuse and co-author Reid Ewing said the recent traffic bumps may also reflect a large infusion along the corridor of new high-rent apartments, whose residents can afford to rely more on cars than TRAX for their daily travel.

(Rick Egan | The Salt Lake Tribune) Traffic on 400 South in Salt Lake City on Tuesday, Jan. 5, 2021.

The study notes that of more than 1,230 new apartments in eight large complexes built along the street, all but a few are labeled as “luxury” and are being leased at market rates, with minimum rents in the range of between $1,050 and $1,340 a month, the study found. Many complexes also offer on-site parking.

So the rise in car travel along 400 South since 2014 is “not surprising,” the study says, given that “the vast majority of people living in these new residential developments along 400 South are not likely to be economically transit-dependent.”

The city has taken significant steps in rezoning land around the TRAX lines on 400 South and North Temple to encourage, among other things, more pedestrian-centered residential development within walking distance of mass transit.

But Ewing, a U. professor of city and metropolitan planning, said the study’s findings suggest that to take full advantage of light rail in reducing congestion and air pollution, Utah cities may also need to mandate more affordable housing along TRAX routes, in what is called “inclusionary” zoning.

A separate U. study of 10 Utah cities that have pursued transit-oriented development in some form found that only Park City has deployed inclusionary zoning, which typically require that a share of affordable units be included in all residential developments, a controversial topic for many private developers.

“I’d love to see [inclusionary zoning] in Salt Lake City,” said Ewing, who noted that elected leaders in Utah’s Capitol are considering the strategy among a set of new housing policies now under review.

Effects of growth

The U. study, conducted at UTA’s behest, is being readied for submission to the Journal of Public Transportation, a peer-reviewed academic publication.

Conducted by Siracuse, Ewing and co-authors Fatemeh Kiani, Sadegh Sabouri and Romello Warren, it updates research done in 2014 that found light rail had reduced traffic along 400/500 South by roughly 10,000 vehicles a day.

Beyond apartment and commercial construction along 400 South since then, several other factors over the past six years have boosted anticipated travel demand along the street that TRAX appears, at least in part, to be alleviating.

The U. campus — one of the state’s top traffic generators — has seen significant expansions since 2010, adding nearly 33,000 students and 23,700 employees and a host of newly constructed buildings at its various colleges and research park.

The study also analyzes what appears to be a massive effect since 2010 on property values within a six-block strip along that east-west TRAX route through downtown and campus, much of it spanned by the city’s transit-oriented zoning.

Its parcel-by-parcel analysis indicates the total value of all residential, commercial and public lots within that area jumped from about $2.2 billion in 1999 to $6.8 billion in 2010. Those land values then rose another $3.2 billion over the ensuing decade to reach $10 billion this year.

You would expect campus growth and development around TRAX to push traffic volumes along 400 South dramatically higher. Yet automobile counts on the stretch are still below their 1999 peak, the study noted, “which shows how greatly TRAX has influenced households’ decision to substitute their mode of travel.”