NEWS

City traffic data shapes future planning

Jenn Rowell
jrowell@greatfallstribune.com

The city is conducting its annual traffic count, in partnership with the Montana Department of Transportation and Cascade County.

Residents will see the counters — many look like hoses in the road — around town during July as the city collects traffic data.

Traffic counts are “the basic data for all transportation decisions,” said Andrew Finch, the city’s transportation planner. “If you ask someone what’s the most important statistic, they’re going to say traffic counts.”

According to MDT, the Traffic Data Collection & Analysis section is responsible for collecting traffic data on about 5,800 active short-term traffic count sites statewide. These counts, also known as coverage counts, make up the bulk of the department’s traffic count program. The continuous count program currently has a total of 99 permanent counters, 62 automatic traffic recorder sites and 37 weigh in motion sites throughout the state collecting traffic data on a daily basis. In addition to providing volume information, many of the ATRs and WIMs provide information such as vehicle length, classification, truck weight data and unbiased speed data.

MDT uses the permanent counters to seasonally adjust short-term counts to estimate annual average daily traffic; provide generalized peak and design hour factors for highway geometric design; monitoring monthly and annual trends; and providing long-term growth factors.

In Great Falls, traffic count data is used for planning purposes such as pavement managements, safety analysis, intersection congestion analysis, roadway capacity, roadway classification, among others.

The locations were set in the 1980s by MDT, but Finch said the city can add locations as needed.

One location that was added a few years ago was 7th Street, just south of 10th Avenue South.

“Traffic has grown on that stretch of roadway, but we didn’t know how it had grown,” Finch said. “That’s why we do these, so we can track changes in the transportation network.”

The data can be plugged into a base year for transportation models that MDT does for the city and those are used for major planning projects or documents like the Great Falls Area Long Range Transportation Plan.

“You have to have accurate traffic counts if you want to characterize what’s going on in the city,” Finch said.

The city takes counts in two consecutive 24-hour counts, then averages the counts using a seasonal adjustment factor that’s set by the state, so that the count can represent any day in the year.

Typically, the highest counts are during the summer, Finch said, and the city always takes their counts around July.

The seasonal adjustments are set for the year in a matrix for each month as well as for different types of roadways since different roadways fluctuate differently throughout the year.

Some residents noticed the counters in the Riverview and Skyline areas and expressed concern that the counts wouldn’t account for school traffic, but Finch said that’s where the seasonal adjustments come in.

“They’re intended to not be biased with school year versus nonschool days,” he said.

“If it’s in an area where during school the traffic is higher and you take the count in July, then the adjustment factor will bump it up,” he said. “On average it’s supposed to represent every day of the year.”

Finch said the city and state do different counts but each agency does their count around the same time of year every year to increase the accuracy of the county for comparing trends.

“If we fluctuated, we would see more variation,” he said.

Jerry McKinley, traffic supervisor in the city public works department, said his division can provide traffic data to businesses looking to open in certain areas or if there’s a request for a new stop sign or school or pedestrian crossing.

They can also measure speeds if they get speed complaints in certain areas.

The data also helps determine when roadways need to be striped.

For example, 36th Avenue Northeast is currently unmarked because it hasn’t hit the usage threshold under federal guidelines to warrant stripes, McKinley said.

The counters are also able to classify vehicle types to track wear and tear on roads, or if certain roads are seeing increased semi-truck traffic that needs to be addressed.

McKinley said he recently attended a workshop in Helena and learned about a system being developed by the state that would allow cities like Great Falls to upload their count data and the system would apply the seasonal adjustment factors, make other calculations and post the data.

“That’s kind of a neat deal for us,” he said.

The city collects, compiles and formats the data and applies seasonal adjustments and other calculations in-house before submitting the data to the state.

Traffic counts are also used to understand accident data, Finch said.

The number of vehicles entering an intersection is factored against the number of accidents and the severity of the accidents are also factored in to develop the list of the city’s most dangerous intersections in the Long-Range Transportation Plan.

“That’s a case of the science of analyzing what’s going on on a roadway,” Finch said. “It’s not just a raw number, we try to rationalize the number. So there are some intersections where you’re odds of getting in an accident are greater than 10th Avenue South.”

Traffic counters also help planners look at peak hour traffic, which was used during planning for an apartment and townhouse project near the city water tower on 36th Avenue Northeast last year.

“Peak hour is pretty important if an adjoining roadway is having capacity problems or an intersection is having problems,” Finch said.

The city also conducts special counts and in June it used special camera counters to track bicycle and pedestrian use in a project with the health department.

Finch said the count will be used as before data for a trails project going in along the Sun River this fall, so the data can be compared to counts after the trails are completed.

One of the biggest ways the city uses the data is for warrant studies, to see if something such as a new stop sign, traffic signal or turn lane is needed.

“We’re responsible for responsible management of taxpayer dollars,” Finch said. “We want to make sure improvements aren’t being put in on a whim, and that it’s going to make things better and that it’s going to be justified.”

Online

To see the city’s traffic count stations, go to http://bit.ly/1H8f1ld.

To see the Great Falls Area Long Range Transportation Plan, adopted in 2014, go to http://bit.ly/1grDX2b.

For more information on MDT traffic data, go to http://1.usa.gov/1ORHmCB.