MoPac managed (TOLL) lanes: A question of safety

Special lanes in Dallas have sharply increased accidents, but engineers say MoPac plan would address flaws.

By Ben Wear

If the state adds two "managed lanes" to MoPac Boulevard north of Town Lake as proposed this month, the increasingly clogged freeway would have a third more capacity and a high-speed refuge for buses, emergency vehicles and motorists willing to pay tolls.

However, given design compromises forced by lack of space, research indicates that the highway would also have more accidents and serious injuries. What is not clear at this point, because little or no study has been done of the particular design contemplated for MoPac (Loop 1), is just how many more accidents.

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The state plans to add lanes along MoPac Boulevard (Loop 1) near 35th Street in Central Austin. But because of space constraints – train tracks, power poles, resolute homeowners – some parts of the inside shoulder of the northbound lanes would be just 15 inches wide.

Officials working on the project say that the design, with the possible exception of an exceedingly tight stretch near Camp Mabry, meets acceptable standards (if not optimal recommendations) and that it is the best approach possible at this point for moving more people in Austin's northwest quadrant.

"If you did not have right-of-way constraints, would you design it differently?" asked Bob Daigh, Austin district engineer for the Texas Department of Transportation. "You bet you would. But that's not the project we have to design. We have to live within those constraints."

The agency hopes to begin construction in late 2008 and have the lanes open two years after that.

The constraints exist only in the southern five miles of the project, between Town Lake and RM 2222, where Union Pacific railroad lines on the inside and a combination of enormous power poles and resolute homeowners on the outside mean the expansion must occur within the Transportation Department's existing right of way.

North of RM 2222, there is plenty of room for expansion, and the state will be able to lay down full 12-foot-wide lanes and spacious 10-foot-wide shoulders.

For that southern section, however, Daigh and his engineers have spent the past year or more trying to figure out how to cram in another lane, plus a buffer of a few feet between the new managed lane on the inside and the three lanes that would remain free. To do that, the design would narrow the regular lanes to 11 feet and have shoulders that typically would be 4 feet wide.

In the worst case — on the northbound lanes of a milelong stretch between West 35th and West 45th streets — the inside shoulder would be a scant 15 inches wide, the managed lane would be just 11 feet wide, and the normal 4-foot buffer separating it from the free lanes would be just 2 feet wide.

For cars using the managed lane in that area, the total side-to-side maneuvering space, including the lane itself, would be just over 14 feet.

The Texas Transportation Institute, in a 2004 study of accidents and designs on Dallas high-occupancy-vehicle lanes where there is typically no inside shoulder, recommended that cars on such segregated, high-speed lanes have 26 feet total side-to-side maneuvering space. That would allow cars to get around a stalled vehicle or one slowing down to move over into the regular lanes.

The "absolute minimum cross-section," the report says, should be 18 feet.

"Without an inside shoulder, when you looked at the crash reports (in Dallas), there just wasn't anywhere for someone to avoid the crashes," said Scott Cooner, an associate research engineer in the Texas Transportation Institute's Arlington office.

The study looked at accident rates on Interstate 35 and Interstate 635 before and after HOV lanes were added. After the HOV lanes opened in 1996 and 1997, injury accidents per million miles traveled over the next four years increased 41 percent on I-35 and 56 percent on I-635.

But as with so many questions about highway safety, any comparison to what might happen with MoPac's managed lanes is necessarily inexact. The state Transportation Department, to some degree because of experience with the Dallas HOV lanes, would build the Austin lanes differently.

On those two Dallas highways, the only separation between the HOV lane and the regular lanes is a double stripe painted on the pavement. Signs tell drivers not to cross those solid double stripes, that movement from the HOV lane to the inside regular lane is supposed to occur only every mile or so, when there is an access point indicated by a dashed line.

On MoPac, the managed lane would be segregated from the regular lanes by a series of closely spaced, flexible plastic pylons. At entry or exit points — and there would be only five, aside from the southern and northern ends — there would be a gap in the pylons of about 1,200 feet, about a quarter-mile, where people could make the lane change.

The reality in Dallas, according to the 2004 report, is that many people have ignored those signs, weaving in and out of the managed lane in efforts to gain advantage or (in the case of people driving alone who are illegally in the HOV lane) to avoid being caught and ticketed. Most of the accidents, Cooner said, occurred because of that rampant lane changing.

The fundamental problem is that cars in the HOV lanes at rush hour, by and large, are going 30 to 35 miles per hour faster than cars in the regular lanes, Cooner said. That speed differential makes lane changes more problematic than on a normal freeway, where everyone typically is traveling at the same speed.

That same problem would exist with the managed lanes on MoPac.

"If you're going to ask people to pay, they have to be going faster," Cooner said.

In fact, the plan with MoPac is to have "dynamic pricing" to ensure that speeds remain high on the managed lane. The tolls to drive in the lane would be significantly higher at peak traffic hours, set at whatever price it took to discourage enough drivers to keep traffic uncongested.

On State Route 91 in Southern California, for instance, the toll for a 10-mile stretch of managed lanes varies between $1.10 overnight and $9.50 between 4 and 5 p.m. Fridays.

The expectation with MoPac is that the pylons, by limiting lane changes to the designated access points, will produce a far lower accident rate than Dallas has seen. In fact, the state Transportation Department is installing pylons on its next Dallas HOV project, on U.S. 75.

"I would certainly feel like your situation is set up to be more successful than what we've had in Dallas," Cooner said.

On the other hand, could funneling everyone who wants to enter or exit the managed lane into a quarter-mile section actually cause more accidents? Cooner said that's an ongoing debate in traffic design circles, one yet to be settled by reliable research.

The bible for U.S. highway design is called the green book, a thick manual published by the American Association of State Highway and Transportation Officials.

It says that on urban freeways, "through-traffic lanes should be 12 ft. wide." On freeways with at least six lanes, such as MoPac, the book says both shoulders should be at least 10 feet wide.

That won't be the case for certain sections of MoPac under the proposal. However, that is already the case near 35th and from Town Lake south to Loop 360 (Capital of Texas Highway). That section south of the river also has shoulders only a couple of feet wide.

The narrower lanes — 11 feet vs. 12 feet — are unlikely to cause any significant increase in accidents, several engineers say. But they could decrease capacity on the regular lanes, because drivers intuitively leave more space between their front bumper and the car in front when the lane is narrower.

The managed lanes could have a similar congesting effect on the inside regular lane, said Elizabeth Jones, an associate professor of civil engineering at the University of Nebraska.

"It's like being in that far right lane where people are entering and exiting," said Jones, a University of Texas graduate who specializes in transportation systems. "You get a little bit of turbulence there, so you don't get as much capacity."

Daigh says this $110 million project is a stopgap solution. A long-term approach, which might involve sinking MoPac belowground like Dallas' Central Expressway, would come much later.

"We cannot wait in this community 10 years to make some improvements" to MoPac, Daigh said. "This is not a silver bullet that will solve all of MoPac's problems. But it is a good step in the right direction."


Peter Stern said...

"Managed Lanes" for MOPAC? Ohhh, you mean toll roads.

"Managed Lanes" = Toll Roads = More Taxes!

That's quite a disguise for toll roads, isn't it? "Managed Lanes" is quite similar to "managed care" only there's no "caring" in most of the Texas Department of Transportation's (TxDOT's) road plans. TxDOT may be a lot of things, but it's certainly NOT community-friendly.

Five years ago Gov. Rick "39-percent" Perry gave TxDOT the "green-light" to become more creative in locating new revenue for building and maintaining Texas roadways. While TxDOT geniuses keep on trying to bilk taxpayers out of their hard-earned money, the agency that's supposed to be working for hard-working Texans is trying to secure top-dollar pay-offs and increased revenue for its wealthy pro-toll lobby.

When are Texans going to get smart and vote-out special interest legislators and [consequently] appointed officials?

The people in charge have no conscience what-so-ever and they don't even try to hide it!

TxDOT engineer Bob Daigh tries to convince us that TxDOT has learned its lesson on road building and that the proposed MOPAC road work will eliminate the problems encountered in the Dallas road work. Can you believe the "chutzpa"? (old wonderful Jewish word for audacity)

Five months ago Mr. Daigh, Area Engineer Don Nyland and the rest of TxDOT approved work on FM 1826 in Hays and Travis Counties. They "resealed" the small 2-lane country roadway with cheaper materials that immediately smeared at intersections from cars and trucks turning there. In addition, TxDOT doesn't put "crowns" on roads because it's more costly --- even though it's the right way to build a roadway. Currently after it rains, FM 1826 is riddled with water and road smears. Obviously, TxDOT doesn't care much about serving and protecting the community from such hazardous conditions. However, TxDOT certainly seems interested in making money for themselves and special interests.

Anyway, what exactly are we talking about with this proposed road work on MOPAC?

MOPAC is an already paid-for with our tax dollars "free" highway on which TxDOT now wants to "improve" by tossing out the train tracks in the middle island and replacing them with a 2-lane toll road ---- errr, "managed lanes". Oh, yes. That will work fine. All the traffic and bottlenecking at strategic locations on MOPAC will be totally relieved by the 2 additional lanes. Dream on. No doubt about it, folks, this is a stupid plan!

Texans need to band together and stop TxDOT from being the "runaway stallion" the governor and legislators have permitted it to be. The Sunset Commission and/or the Travis County District Attorney's Office should follow the money and paper trails that TxDOT has left and eliminate any doubt in the public's mind that TxDOT is acting questionably and/or illegally in many of the wheelings and dealings it has and is making with privateers. Something doesn't smell quite right in Central Texas and it's not from our oversized vehicles burning high-priced gasoline.

Stop the toll road / "managed lane" fever crusading in Central Texas by contacting elected officials. What happens here will occur throughout the state. That's NOT a tax legacy we want to leave to generations of our children's children.


Anonymous said...

In my opinion, the best solution for Mopac is to have the existing railroad tracks ripped out, then add a 4rth continuous lane, so that Mopac is 4 full lanes from Parmer to William Cannon. Without the railroad tracks, there would be nice wide shoulders on each end, and maybe even a little room for an HOV lane (5 lanes total in each direction). This would also have to include expanding the bridge over Town Lake (why even add lanes to Mopac without addressing Mopac's worst bottleneck at Town Lake???). However ALL of this new capacity should remain FREE for drivers.

Why is every single new freeway initiative in this town proposed as a freakN toll road???!?!?!? San Antonio was able to expand Loop 410 and it remains FREE, Houston is expanding Interstate 10 West (Katy) and it will stay FREE. Dallas was able to expand US75 (Central Expressway) and it's still FREE. Even the multi-gazillion dollar high five interchange (LBJ @ US75) is non-tolled.

Again, WHY does every single new expressway in Austin have to have a toll!?!?!?!?!?!?!

Anonymous said...

Maybe the republican politicians try this managed and toll lane crap in austin because most of us are democrats or independents and wouldn't vote for Perry anyway. If they tried this in a more republican town they'd lose more votes more quickly.

Sal Costello said...

The Statesman endorsed the unpopular Phase II tolls (tolls on our freeways) in 2004, and left all the heavy lifting to the public.

This turn of events, and some real reporting on the managed (toll) lanes is good news. Too bad the Statesman does not always stand with the people.

We'll take what we can get.


Sal Costello said...


I got a bill in the mail for a toll fee. I called the number on the bill. I apparently called 1-800-468-9824 instead of 1-888-468-9824. I was told to call 1-800-377-talk. You can probably guess the rest. It was a porno talk line. Are any of the tollway big shots in bed with the porno industry?

Anonymous said...

What the heck do we pay taxes for if every time we need something (like basic road expansion) we are being charged (AGAIN) for it? Sounds like a jack to me... This is clearly one of those times that folks need to stand up and say NO MORE!