Inside Seven
Current Issue: September 2014
article
Feature

New Non-Skid Treatment Gains Traction on Sepulveda Ramp
by  Kelly Markham
Issue Date: 03/2011

How District 7 is transforming an often-closed ramp in a high-profile location into a smoothly functioning facility with friction to spare.

[Click on photos to enlarge and read captions.]

Most ramps in District 7 perform their roles perfectly, gently shuttling motorists on and off freeways without incident. But then there is the Sepulveda Boulevard on-ramp to the eastbound Glenn Anderson Freeway (I-105). This ramp cannot meekly do its job like its brethren. It’s the problem child of the bunch, the ramp that has arguably prompted more angry phone calls to Caltrans than any other. But to be fair, it’s not the ramp’s fault.

“The ramp isn’t dangerous, but it posed a safety risk when drivers were ignoring prudent speeds during wet weather,” said Yunus Ghausi, senior transportation engineer, Office of Traffic Investigations. Wet weather plus imprudent speeds equals potential accidents, which is why the California Highway Patrol has frequently asked Caltrans to close the ramp, hence the angry phone calls.

Closing ramps is not something Caltrans does lightly, particularly when the ramp in question is one of the key ramps near Los Angeles International Airport, the busiest airport in the western U.S. That’s why last October, a temporary fix was implemented to reduce closures. “We restriped the ramp to one lane to keep speeds down and eliminate unsafe passing. We’ll restripe it back to two lanes after the HFST project,” said Ghausi.

The HFST project, the first in District 7, should change everything.

HFST stands for high-friction surface treatment, also known as anti-skid surfacing. HFSTs are composed of tough, abrasion-resistant aggregates bonded to the pavement surface using an epoxy-resin. The resulting surface is rough, hard and durable and increases what’s known as the coefficient of friction. Translation for non-engineers: It’s a thin, super-grippy layer that prevents cars from skidding, especially in wet weather.

“When the project is complete, the expected coefficient of friction on the ramp will be very high – among the highest in the district,” said District 7 Materials Engineer Kirsten Stahl.

This capital improvement project, scheduled for this month, is a quick one, taking less than a week and costing about $134,000. Applying the non-skid surface is a relatively simple procedure, but one that’s fairly fussy in terms of acceptable weather conditions. It must be at least 50 degrees to proceed and very dry.

“The first thing we’ll do is clean the pavement, get rid of all the oil and dirt,” said Resident Engineer Mashhur Ali. Then, once the pavement is dry, a thin layer of epoxy-resin – about an eighth of an inch – mixed with aggregate is applied to the surface. Once the mixture cures (it takes about two hours), the ramp will be restriped.

Total project duration: about three or four days. Benefit to Caltrans and motorists: shorter stopping distances, greater traction, better vehicle control, reduced accident rates, happier motorists and fewer angry phone calls. In short, it’s a fast, simple project that will enhance safety and reduce ramp closures.

So why have we not used HFST more widely in District 7? “It’s still in an evaluation phase, and there seem to be issues getting the correct bauxite aggregate,” said Stahl, referring to the typical aggregate used for HFST projects.

Caltrans staff will be watching the Sepulveda ramp closely to see how the district’s first HFST performs. Additional locations may be identified for similar treatments in the future. In the meantime, the next time you’re leaving LAX headed east on I-105, check out the Sepulveda ramp. Be sure to drive at a prudent speed, and enjoy some of the finest friction in the district.

 

Crews will apply a non-skid overlay (called a ''high-friction surface treatment'') to the Sepulveda on-ramp to eastbound I-105 this month to reduce weather-related closures. CHP frequently requested that the southbound Sepulveda ramp to eastbound I-105 be closed in wet weather to prevent accidents. [Note: This photo shows the ramp before it was restriped to one lane in October.] Workers apply aggregate to a curved section of roadway as part of an FHWA demonstration project in Florida. HFSTs, like this one applied on an FHWA demonstration project, improve vehicle traction and reduce skidding.