These are the Boise area’s 10 busiest highways. Is your commute on one of them?

·8 min read
Sarah A. Miller/smiller@idahostatesman.com

Is it just you, or is your commute to work getting longer and longer every year?

Turns out, some roads are getting busier than others.

This may come as no surprise to people who’ve experienced development in their own backyard: Population in the Treasure Valley grew by nearly 27% from 2010 through 2020, according to the Community Planning Association of Southwest Idaho.

With an increase in population comes an increase in traffic, accompanied by either more development or congestion (or both).

This increase is despite the volume of people choosing to work from home since the start of the COVID-19 pandemic in 2020. Some streets saw traffic counts decrease significantly that year, especially traffic on the Interstate 184 Connector to downtown Boise and around Boise State University.

Some state highways have become notorious for attracting development and having high traffic volumes.

So which are the busiest roads in Ada and Canyon counties? Which have the fastest growth in traffic? And which are the most congested at rush hour?

The first answer is easy: Interstate 84 still reigns as the state highway with the most traffic.

The fastest-growth award goes to Meridian Road, with a 27% increase since 2016.

And first prize, or rather the booby prize, for congestion goes to Franklin Road at Chinden Boulevard. Note that there are three Franklin Roads in the two counties; we’re talking about the north-to-south road that’s north of Nampa in Canyon County. More on that below.

The Treasure Valley’s busiest roads

Here are the top 10 roadways with the highest traffic counts in the two counties based on the most recent data from 2018 to 2021.

This list includes highlights of congestion problems on many of these roads. A caveat: Not all congested roads have high traffic counts, and not all high-traffic roads show signs of congestion.

1. Interstate 84

According to Compass, this interstate sees the largest volumes of vehicles in the entire state. The freeway segment between the Eagle Road interchange and the I-184 Flying Wye interchange has an average traffic count of over 150,000 vehicles per day.

Average traffic in 2013 was recorded at 120,000 by ACHD, meaning there’s been an increase of 30,000, or 25%. Compass predicts that travel demand on this corridor will double by 2035.

Compass prepares annual congestion reports. The most recent covers 2020, but we looked at 2019, because 2020’s COVID-19 shutdown and the accompanying surge in work from home skewed the 2020 data.

Compass’ 2019 report says I-84 is most congested during midday at the eastbound off ramp to Karcher Road (Exit 33). That is also the second-most congested road segment in Ada and Canyon counties.

2. Interstate 184 Connector

An average of 83,527 vehicles travel between the Curtis and Franklin road interchanges on the I-184 Connector every day, according to data from ACHD. But traffic has increased by just 3% since 2015.

If you’re a downtown worker who lives to the west, this will come as no surprise: According to Compass, the highest congestion on the Connector typically occurs where it merges with westbound I-84 and “is caused by commuters leaving the city of Boise at the end of the work day.”

3. Eagle Road

The segment of Eagle Road stretching from I-84 north to State Street serves 54,100 vehicles per day, according to ACHD. That’s just a 2.7% increase since 2016. The stretch also includes some of the highest-volume intersections in the state, according to Compass.

Also called State Highway 55, Eagle Road has long been the busiest non-interstate highway in Idaho.

4. Front Street

Beating Chinden Boulevard by just 1,100 vehicles, Front Street in downtown Boise carries 39,800 vehicles a day between Capitol Boulevard and 13th Street, according to ACHD. In just five years, that number increased by 9.6%.

Front Street’s eastbound counterpart, Myrtle Street, also has five lanes and served 33,796 vehicles per day in 2019.

Most of the westbound traffic from Front Street flows into the westbound Connector, while the Connector’s eastbound lanes flow into Myrtle Street.

The westbound one-way street’s five lanes result in significantly lower congestion than on other Ada County roadways with similar counts.

5. Chinden Boulevard

With an average daily traffic count of 37,900, ACHD traffic numbers show a 5% increase in traffic on Chinden Boulevard from Glenwood Street to Curtis Road since 2014.

According to Compass, the highest traffic volume is between Curtis Road and Orchard Street in Garden City.

Chinden from Cloverdale Road to Eagle Road was the No. 3 most-congested spot in 2019.

6. Glenwood Street

The busiest part of Glenwood Street is between Chinden Boulevard and State Street, with the same average traffic count as Chindren’s: 37,900 vehicles per day, according to ACHD.

However, Glenwood started out much busier than Chinden. Glenwood has had only a 0.3% increase in traffic since 2012.

7. State Street

Despite being one of the streets with the highest traffic volumes in Ada County, traffic in State Street has actually decreased by 9.5% since 2015. ACHD credits that to “COVID impact.”

From Veterans Memorial Parkway to Bogart Lane, the most recent daily traffic count is 35,400. In 2015, the count was 39,100.

8. Ten Mile Road

The busiest stretch of Ten Mile Road is from I-84 to Cherry Lane, at 35,000 vehicles per day, compared with 33,700 in 2017, according to ACHD.

The segment at the I-84 overpass is among the top 10 most-congested road segments in the Treasure Valley during morning rush hour.

9. Meridian Road

The most recent traffic count, 34,800 vehicles per day, was recorded for the segment from I-84 south to Deer Flat Road. North of the freeway, 23,694 vehicles per day were counted between Franklin Road and Fairview Avenue.

The two most congested parts of Meridian Road are at the I-84 southbound overpass during afternoon rush hour, and the eastbound I-84 on ramp at Exit 44 during morning rush hour. ACHD recorded traffic at 50,882 vehicles per day just north of the overpass in 2019 and at 18,216 on the eastbound I-84 on ramp.

10. Curtis Road

The segment of Curtis Road stretching from Chinden Boulevard south to Fairview Avenue has an average traffic count of 34,600, which is 4.5% greater than the 2014 count of 33,700 vehicles, according to ACHD.

The busiest street segment is at the Chinden intersection.

Congestion and rush hour

Do you see your commute route on the Top 10 list? The good news is this: During peak traffic hours, the route you take matters.

According to the Ada County Highway District, morning peak hours are from 7 to 9 a.m and afternoon peak hours are from 4 to 6 p.m.

Under free-flow conditions in 2019, driving from Boise to Caldwell via U.S. 20/26 (Chinden Boulevard) would take 28 minutes. The average afternoon traffic congestion on Chinden added 22 minutes to the commute, resulting in 50 minutes of travel time.

On the other hand, traveling from Boise to Caldwell via I-84 around the same time of day lengthened the 22-minute free-flow commute by nine minutes of congestion, totaling at 31 minutes of travel time.

Remember the booby prize for congestion awarded to Franklin Road in Canyon County? Specifically, we’re talking about the southbound segment of Franklin as it approaches Chinden during the morning rush hour. It takes almost four times longer to drive than in free-flow conditions.

Franklin Road’s southbound junction with Chinden showed the highest levels of congestion going as far back as 2004, according to congestion data from Compass.

What the future holds

The traffic congestion we see today on Ada and Canyon roadways is evidence of an increasing demand on the transportation system. Brace yourself: It’s going to get worse, at least west of Boise.

According to Compass Principal Planner Hunter Mulhall, future development in western Ada County and Canyon County will bring “a lot more congestion” to the Treasure Valley in the next four years.

“We just haven’t been able to quite keep up with building the roads out there … those aren’t necessarily built to handle the development at this point,” Mulhall said.

Future planned projects, such as expanding State Street from five to seven lanes, aim to lessen congestion.

“Adding lanes is just one way we can help with traffic congestion,” Mulhall said. “We’re not always looking to add more lanes. I’s not always the first option.”

Additional developments will focus more on drawing people away from the roads and onto bicycle lanes by building more bicycling and pedestrian infrastructure, he said.

But more lanes are on the way on an increasingly busy segment of Interstate 84. The Idaho Transportation Department is widening I-84 to three lanes in each direction between the Franklin Road interchange in Caldwell and the Karcher interchange in western Nampa. ITD expects to finish construction in 2023.

“We’re already thinking ahead and saying, ‘Well, we’re probably not going to add another lane anytime in the next 13 years,’” Mulhall said. “So what can we do in the meantime to keep traffic flowing and moving through efficiently?”

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