Tribal Trail Road traffic impacts

A modeling tool that will test “what if?” scenarios for the future of Teton County’s road network is finally ready for prime time and has produced some of its first results analyzing the potential Tribal Trail Connector.

The model was created by a team of Cambridge Systematics in Denver. Teton County, the town of Jackson and the Wyoming Department of Transportation split the $150,000 cost of developing the model.

“My takeaway is that the model is a robust planning tool and is well calibrated,” Interim County Engineer Amy Ramage said.

The computer program will allow transportation officials to test the effects of various scenarios on the local road network, such as adding a new subdivision, road link or bus route. It uses WYDOT traffic counts, employment and housing studies, lodging inventories and “big data,” aggregated and anonymized information purchased from GPS and cellphone companies.

Cambridge performed a “test run” of the model examining the effects of the Tribal Trail Connector on existing traffic conditions. The connector is a capital project identified in the town and county’s 2015 Integrated Transportation Plan, with goals to provide redundancy and relieve congestion at the “Y” intersection at Highway 22 and Broadway.

A Tribal Trail Connector with a 35 mph speed limit would see 3,400 vehicles per day, according to the model’s test. The parallel route on Highway 22 would see 2,300 fewer vehicles per day.

“What that really showed us is that the bulk of traffic on the Tribal Trail extension is coming from local traffic, traffic in the specific neighborhood,” Cambridge consultant Sean McAtee said.

Many neighbors worry the connector would attract substantial “through” traffic, disrupting a residential area and school zone. McAtee said his team tested whether there was a scenario where the model placed 9,000 vehicles a day on Tribal Trail, but the only way that would happen is if the road were a bypass with a speed limit of 65 mph.

“We’re also seeing that we’re not observing a lot of cut-through traffic,” he said. “We’re finding that with that new connection, it does not become an attractive alternative route or bypass.” It’s still faster and easier, he said, for most drivers to head north to the “Y” and make a left onto Highway 22.

Ramage cautioned against reading too much into the test scenario results.

“We will need further analysis with micro simulation of various options for intersections for the Tribal Trail project and for several town of Jackson projects,” Ramage said. “Because it’s a dynamic tool, the output will change as we change intersections, lane configurations, speed limits, etc., so I think the test cases are accurate with what we have plugged into the model at this point.”

Cambridge Systematics has pitched the town and county on purchasing an additional software upgrade to allow for “micro simulation” at a level of finer detail.

Responsible Growth Coalition board member Geoff Gottlieb, a staunch opponent of the connector, said the model’s preliminary results validate his view that adding the Tribal Trail link doesn’t make sense.

“What it boils down to is the only people who are going to be using the Tribal Trail Connector are people who live in the affected area,” Gottlieb said. “Does that justify the Tribal Trail Connector road? Most of the people in those neighborhoods don’t want it.”

Gottlieb said the estimated cost of $7 million isn’t worth the pollution, habitat destruction and extra cars on the road that the connector would bring, especially if it will only see limited use. Responsible Growth Coalition has consistently pressured the county to wait for the delivery of the traffic model before determining whether Tribal Trail is needed.

County Commissioner Mark Barron said to adequately interpret the model’s Tribal Trail results it would be necessary to look at what it says about vehicle counts on other Jackson streets.

“Isolating them and not giving those road counts in a larger relationship with other Jackson streets could be problematic,” Barron said. “What’s the traffic count on Snow King? Redmond? Kelly? East Broadway?”

Ramage said the test run’s estimated Tribal Trail volumes are less than forecast in previous studies.

She said planners “will be looking very closely” at traffic numbers and how a new intersection at Highway 22 and the connector would affect traffic flow throughout South Park.

Teton County hired WYDOT to take the lead on planning and engineering for the Tribal Trail project, and WYDOT recently hired consultants to perform the work, but the process is just getting started. Teton County has also appointed a stakeholder group.

The contract originally anticipated that Cambridge staffers would train town, county and state transportation officials how to use the software, but a lack of staff time means negotiations are underway to pay Cambridge to continue to operate it for local engineers.

Contact Allie Gross at 732-7063, county@jhnewsandguide.com or @JHNGcounty.

Allie Gross covers Teton County government. Originally from the Chicago area, she joined the News&Guide in 2017 after studying politics and Spanish at Vanderbilt University in Nashville.

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(3) comments

Kathy Tompkins

Do the people who say build it because we can...Seven million plus on a little road to subsidize more single occupancy vehicles that will lead to a bigger road in short order, once drivers fill that road. Remember, there is no money to rebuild High School Road to handle new traffic. More taxes needed for that. One way in and out of Corner Creek Lane. Middle School Road already at D service at critical times of day. Diesel pollution from unregulated commercial vehicles will get worse. You can see the heavy fog from vehicles on cold days around schools, playgrounds and athletic fields. Also no one figured in the plans to create more density by increasing industrial commercial and residential units on Gregory dumping out onto High School Road creating more pollution and traffic. It already smells awful and makes you cough. Think what it does to kids running around playing. There is increased asthma and cognitive issues connected to busy roads next to schools. So build it anyway without waiting to replace Snake River Bridge and widen 22 along with the improvements already working at the Y just because you can? Must be you don't mind the never ending increase in taxes for at best an over subsidized short term fix. That money can be better spent on fixing old roads and neighborhood infrastructure that is sorely needed. Wait for the state with fed money to pay for SR Bridge and 22 improvements in near future and already having public meetings on. WYDOT has already stated 22 expansion will be implemented. So you want to put in a road that will have to torn up at twenty two when the widening takes place? Way to waste more money by putting the tiny cart before the big Klidesdale.

Kathy Tompkins

Correction (To) the people who say build it because we can...

Geoff Gottlieb

In my conversation with Allie, I did not add "especially if it will only see limited use". That would imply that if the model had projected significant use, then I would be in favor of the $7mm expenditure. I would not be.
To clarify RGC's position: to date there has been no analysis that demonstrates benefits to the community with the TTCR's construction that justify its cost and potential risks to the environment. Those risks are (1) disruption of the habitat the road will cross, and (2) the pollution and noise created by the increased number of vehicles that will be circulating as a result of induced demand triggered by the road itself. The model run, illustrated in the diagram above, indicates a net induced demand of 1100 vehicles per day.
The use of the connector will be dominated by local South Park residents, who as a group overwhelmingly oppose its construction. That does not mean that if it is built anyway, they won't use it.

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