Why Is MoPac Traffic So Much Worse Southbound In The Afternoon Than Northbound In The Morning?

Jan 10, 2019

Every weekday, hundreds of thousands of commuters flood Austin-area roads and highways with more traffic than they’re designed to handle. Some commutes are worse than others, depending on the time and where a driver is heading.

Tim Ziegler’s drive to work north on MoPac in the morning is a relative breeze, for example, compared to the time it takes him to get home south along the exact same route.

Tim Ziegler wanted to know why his afternoon commute on MoPac is so much worse than his morning commute. So he asked our ATXplained project about it.
Credit Gabriel C. Pérez / KUT

“When I go to work, it only takes me about 20 minutes to get from my house in Bouldin Creek all the way up north of [Highway] 183,” he says. “But then going home every day it takes me about 50 minutes or sometimes even more than an hour. So, I was wondering: Why would there be so much more traffic coming home than going on the way to work?”

Ziegler says he noted the discrepancy in his morning and afternoon commutes times even before the variable toll lanes opened in each direction between Parmer Lane and Cesar Chavez in 2017. Now, the difference is just easier to track due to the highway signs that flash the fluctuating prices.

“In the morning, the toll going north is only 25 cents, pretty much every day. ... And then on the way home it's always like 6,7,8,9, 10 bucks,” he says, depending on how bad traffic is.

According to the CTRMA, Thursday is typically the busiest weekday for commuters on the roadway. However, the early afternoon surge in traffic illustrated above is likely due to holiday travel associated with the upcoming Christmas holiday weekend. Travel speeds, times and toll rates vary by time of day, day of the week and direction of travel.
Credit Central Texas Regional Mobility Authority
Bottlenecks Over The River

The Central Texas Regional Mobility Authority manages the roadway and sets toll prices based on traffic speed and volume. Community Relations Director Steve Pustelnyk says Zeigler’s morning and afternoon commute times are different because MoPac is basically a bottleneck over the river downtown.

“In the morning, there is congestion on MoPac northbound, but it’s south of the [Colorado] River," he says. "And as soon as you hit the river and you hit downtown – I’m just throwing out a rough number – about 30 percent or so of the traffic exits into the downtown area.”  

Pustelnyk says that makes traffic that much lighter after crossing the river going north.

A huge chunk of traffic exits MoPac in the downtown area.
Credit Gabriel C. Pérez / KUT

Kara Kockelman, a transportation engineering professor at UT Austin, says another reason Ziegler’s commute is worse heading home is that drivers, in general, have more destinations in the afternoon.

“They’re not just returning from work and school or sports teams practice after school and extracurriculars," she says. "They’re heading out on the town for dinners and to see friends and families and to pick up kids from other activities."

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Even with the added toll lanes, she says, MoPac still gets backed up because CTRMA hasn't expanded the traffic capacity crossing the river.

“In fact, we’ve sort of limited it because we’ve taken over one of the lanes for exclusive use by the express lane. So that limits flexibility across the lanes a little bit," Kockelman says. "It makes the capacity a little bit worse going southbound across the river."

Another major factor slowing down MoPac, she says, is I-35, which cuts through the other side of downtown.

People who live in the region avoid 35 "because it is such a major bottleneck and that leaves only MoPac that’s another north-south [option]," she says. "So we don’t have a lot of choices and I-35 is already pretty full with trucks and people who must use that corridor.”

Congestion Pricing Systems

Increasing traffic capacity on MoPac by adding more lanes, however, is not a long-term solution to eliminating congestion, Kockelman says. The only viable fix, she says, is turning all lanes of Austin’s busiest roadways into toll lanes. The system would be similar to carbon tax proposals that seek to reduce greenhouse gas emissions by creating a marketplace for pollution output.

"You can't sell ice cream on a road where all the other ice cream in all the other shops is free."

“You can call it value pricing,” she says. “It’s basically tolls that go up and down with congestion, not just to keep traffic moving but to really reflect what is that actual cost that you are imposing on others when you join the roadway?”

Kockelman says that nearly all the revenue generated by such a toll system would go back to drivers as a form of credit, reflecting the cost of driving during peak hours.

“So [drivers] would have a budget each month to spend on the transportation network," she says, "and if they avoid those congested times of the day, those congested links, they’ll have money every month that they can spend on other things like renting bikes and Uber or Lyft.”

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Kockelman says one reason the current toll system on MoPac is ineffective is because all the other lanes on the 11-mile stretch are still free.  

Cars line up on an entrance ramp to MoPac.
Credit Gabriel C. Pérez / KUT

“You can’t sell ice cream on a road where all the other ice cream in all the other shops is free. So, you really do need to price it wherever there is congestion so the market should exist for that scarce road space," she says.

Congestion-pricing systems are rare, but have shown success in places like London, Stockholm and Singapore. Austin, however, is not likely a place where the extra taxes and public surveillance needed for such a system will be accepted any time soon.

In the meantime, Ziegler says sitting in traffic gives him lots of time to think about other options for getting to and from work: like taking the 980 Rapid Bus that runs up and down the MoPac express lanes or riding a bike to catch the MetroRail to work and back.

“Actually, I don’t really know if it would save me that much time," he says, "but being on a train is much better than driving a car because you can read a book or you don’t have to be like, hands gripping the wheel.”

Follow Joseph Leahy on Twitter: @joemikeleahy

 

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