Even on a warm and dry day, motorists with even a slight fear of heights get a bit queasy when taking the Loop 820 exit to Interstate 30 heading into Arlington.
But when the weather is rainy or icy, the highway exit ramp to I-30 can feel downright treacherous.
“When you are on 820 and exit on 30 toward the ballpark, it is super high. But more importantly, halfway across the bridge on the left side, there is a splattering of red paint on the concrete side which always looks like a nasty murder,” joked Brian Ketcham, a Keller teacher who sometimes takes that route to Texas Rangers baseball games.
117 feet Height of tallest ramp on the “High Five” interchange of U.S. 75 and I-635 in Dallas.
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Keeping motorists safe on the region’s highway ramps — in good weather or bad — has become quite a tall order.
The region is now home to 10 interchanges that are 81 feet or taller — and nine of them have been built in roughly the past 15 years.
The very highest point is on the LBJ/U.S. 75 interchange in Dallas known as the “High Five,” where the eastbound LBJ ramp to northbound 75 clocks in at 117 feet above the ground.
I would not want to live in one of those houses below.
Jamie Terrell, east Fort Worth
The Fort Worth area also has more than its share of skyscraping ramps, including the I-35W/I-30 “Mixmaster” in downtown Fort Worth, where the northbound I-35W ramp to westbound I-30 registers 110 feet tall.
Keeping them dry
When bad weather looms, these are the first places Texas Department of Transportation crews go to look for signs of ice.
“We have 225 personnel available to work in 12-hour shifts, and they will be focusing on bridges and overpasses,” said Val Lopez, spokesman for the department’s Fort Worth district, which cares for highways and bridges in nine counties on the region’s west side. Sometimes, the agency receives reports that cars and trucks (particularly 18-wheelers) are beginning to slip on the highway ramps, and the department closes them to prevent other traffic from trying to use the ramps.
Other times, the Transportation Department’s workers themselves notice ice forming on the bridges and call local police to request help with an immediate ramp closure.
But generally, the goal is to keep the ramps open and flowing with traffic.
The department typically uses a liquid salty brine to spray on ramps and bridges as a pre-treatment to prevent ice. When the brine dries, it forms a thin, salty residue on the roads that can dramatically drop the freezing point of precipitation that lands on driving surfaces.
But if the storm is big enough, ice and freezing rain can wear away the brine residue, and when that happens highway maintenance crews use a combination of sand and magnesium chloride, a reddish rock salt mined in Utah’s Great Salt Lake region, to melt ice on the surfaces.
The North Texas Tollway Authority, which operates the region’s toll roads including Chisholm Trail Parkway in southwest Fort Worth, uses similar tactics to prevent icy buildup on its ramps. Five of the 10 tallest road structures in North Texas are tollway ramps.
In some parts of Dallas-Fort Worth, the highway interchanges are so tall it’s like driving on the roof of an 11-story building.
Even on a dry day, it can be a real source of tension to drive on a roadway that tall — especially if someone has a fear of heights.
“I would not want to live in one of those houses below,” joked Jamie Terrell of east Fort Worth, who along with Ketcham took part in a Facebook discussion of tall ramps.
New design methods
Tall interchanges are becoming more common in North Texas in part because of new road design methods.
For example, engineers learned through trial and error that old cloverleaf-shaped freeway ramps at ground level — which were common on roads built in the 1950s and ’60s — couldn’t efficiently move large numbers of cars, said Tony Hartzel, a Transportation Department spokesman.
Instead, it was preferable to separate cars on a larger number of ramps, with each one taking motorists in a specific direction. But as a result of that new design, interchanges now typically feature many more ramps than their predecessors, and the structures tend to get taller as the ramps are stacked in layers.
The “High Five” in Dallas is so named because it has roadways on five levels.
There really is no limit to how tall an interchange ramp can be. However, generally the taller they are the longer the ramps have to be. For example, Hartzel said, one of the “High Five” ramps is nearly 2 miles long.
Tallest in Texas
Although the tallest freeway interchanges tend to be in densely populated areas, that’s not where you’ll find the truly highest roadways and bridges in Texas.
For example, the Pecos River High Bridge, which carried railroad traffic in the Big Bend region, is 322 feet above the remote gorge it crosses.
For automobiles in Texas, it can’t get much taller than the Rainbow Bridge near Port Arthur, which is 176 feet tall, Hartzel said.