The afternoon drive home is slower, but the morning commute on Interstate 380 between Cedar Rapids and Iowa City is more intense, said a Cedar Rapids couple who have grappled with I-380 rush hour for more than a decade.

Tailgating is common because weavers exploit even small gaps to dart between lanes, husband Randy Roeder said. Phantom disturbances lead to time-sucking backups, wife Nancy Kraft said. Once or twice a week, crashes screech travel to a halt, they said.

“A lot of times, we’ll have a slowdown or a stop, and by the time you get (to the origin of the problem), you don’t know what happened,” Kraft said. “We can be an hour late.”

The four-lane I-380 (two north and two south) between Cedar Rapids and Iowa City is one of Iowa’s busiest, most-crash-prone stretches. Delays of 20 minutes or even an hour are common. It’s the Corridor’s sample-sized dose of big city problems.

A 2014 study found congestion had been growing on urban interstates in Iowa, though it still was less than in 31 other states.

The Iowa Department of Transportation has said I-380 should be widened to six or eight lanes, but that hasn’t been added to its five-year highway plan. Some preliminary steps are being taken, however.

The Iowa DOT is designing a six-lane section from I-80/380 through the new Forevergreen Road interchange in North Liberty, which could be complete by 2019. And the Iowa DOT has begun a 12-to-18-month study for adding capacity, or lanes, in each direction on I-380 from the Iowa River to just short of Highway 30, said Cathy Cutler, an Iowa DOT transportation planner.

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The study will include environmental analysis and whether lanes should be added on the median side or shoulder.

Crashes and other traffic incidents, such as broken-down vehicles, account for 50 percent of congestion in Iowa, according to the Iowa DOT. One minute of a blocked lane leads to about four minutes of delay, according to the agency.

In the past 18 months, 380 from I-80 and milemarker 25 in Hiawatha has accounted for 611 crashes — more than a crash per day, or 16 crashes per mile each year, according to the DOT.

The Iowa DOT Traffic Management Center doesn’t track delay time specifically, but clearing an “event” averaged 60 minutes for the 230 accidents reported.

Congestion costs Iowa $380 million per year in wasted time and fuel, including $536,000 on I-380 in Cedar Rapids in July, according to the DOT.

“Whenever we have an incident, that is reducing capacity on the interstate,” said Scott Marler, traffic operations director for the DOT. “That is precisely why we are seeing the backups we are seeing, and it is one of the reasons we look to clear an incident as quickly as we can.”

Each minute of a traffic incident increases the likelihood of a secondary crash 2.8 percent, and might account for 20 percent of all crashes, the agency concludes.

For example, a crash occurred at 6:30 a.m. Nov. 17 on northbound I-380 near the Highway 30 interchange. At 7:21 a.m., a secondary crash occurred five miles away near Swisher. Within 25 minutes of the secondary crash, the average speed had dropped to 32 mph and traffic had backed up three miles. The incident was cleared and the traffic flow was back to normal by 8:30 a.m.

Roadway debris, roadwork and gawking at disruptions also contribute to backups. Another troubling dynamic is a dangerous flow on I-380 where the left lane moves 78 to 82 mph, while the right lane moves at 70, Roeder said.

“You don’t want to be in the right lane because it moves really slow with people merging,” Roeder said. “But in the left lane, you have people cutting in three feet in front of you.”

Patrick Hoye, bureau chief of the Governor’s Traffic Safety Bureau, said the high volume of traffic leads to more backups. He also said the speed variance on 380 is higher than normal.

“Is there any way to reduce the crashes in an area?” Hoye said. “Do you need additional lanes? That seems to be one way to ease congestion. But sometimes it just really is not a whole lot you can do with certain roads.”

Population increase

The corridor population has grown, and so has the traffic. In the past decade, the population has risen 13 percent in Linn and Johnson counties to about 355,000 people, according to the most recent data from the U.S. Census Bureau. Licensed drivers climbed 31 percent in those counties from 2007 to 2014, according to the Iowa DOT.

Traffic on I-380 has spiked to almost 87,000 vehicles a day in Cedar Rapids, up 4 percent in 10 years, and 50,000 to 57,000 vehicles a day from I-80 to Highway 30. That is 24 percent growth at some points, according to the Iowa DOT.

Crash rates on I-380 are substantially higher than statewide averages. On average, municipal interstates have 9.73 crashes per mile, per year, while rural interstates experience 3.44 crashes per mile, per year, DOT data show.

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Another data set shows crash rates on I-380 are well below other population centers in Iowa, such as 42 per mile, per year on 35/235 and 27 per mile, per year on I-80 around Des Moines, West Des Moines and Ankeny. The rate is 33 per mile, per year on Interstate 74 near the Quad Cities.

Comparisons

It’s difficult to evaluate traffic relative to other areas, Marler said.

The DOT is developing “more direct measures as part of our strategic approach to managing Iowa’s highways, to look at how the system operates,” he said.

This would include a way to measure congestion. That should be ready within a year, Marler said.

“We see incidents occurring on 380, and anywhere with that amount of traffic flowing has a potential to cause a backup, just like in what we see in the other metropolitan areas,” he said, noting it can occur in rural areas, too.

The Iowa DOT is pursuing a variety of transit alternatives to curb congestion on I-380, including an express bus services from Iowa City to Cedar Rapids, van pools, ride-sharing programs, and park-and-rides to help ease I-380 traffic. Driving the alternatives, in part, is a major I-80/380 mixmaster replacement that will further disrupt traffic. In addition, CRANDIC, local municipalities and the Iowa DOT are funding another passenger-rail feasibility study.

“I would take light rail,” Kraft said. Roeder chimed in, “Her husband would prefer six lanes.” Kraft continued, “But I think most people would stick to their cars.”

The DOT’s Cutler noted that “studies did not conclude other modes would prevent the need to add additional highway lanes.”

A recently passed 10-cent-per-gallon gas tax provides more revenue to take on such projects, but the Iowa Transportation Commission has prioritized widening highway corridors, including Highway 20 in northwest Iowa, 30 in Benton and Tama counties and 61 in Eastern Iowa.

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Also factoring into priorities are road conditions, the percentage of trucks on the road and availability of alternative routes, said Steve Gent, director of traffic and safety at the DOT. He noted the Iowa City-Cedar Rapids Corridor lacks the alternate-route options other population centers have.

“We are at that point we need to six-lane 380,” Gent said “It’s an overall priority for us.”