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Department of Transportation

Federal Highway Administration

by: Acting Director, Office of Safety Design

For more than 50 years, these barriers have been a common feature along California highways, keeping vehicles from careening across freway medians into oncoming traffic or veering off a steep curve into a canyon or creek. For Caltrans engineers, the barriers - steel cable, steel beam and concrete - have literally been lifesavers. The debate over the appearance of highway barriers, however, is not that simple.

On one side are the traffic safety engineers and maintenance crews who have to maintain the barriers. On the other are the public and the Caltrans professions whose job it is to protect the environment and enhance the aestheic quality of the transportation system.

"The safety value of highway barriers is without question," says Jack Broadbent, Senior Landscape Architect in the Office of Landscape Architecture.

But that is where the unanimity of opinion ends. "The highway system is like a hallway in your home. Most people prefer some pictures of wallpaper to a gray, blank wall. It really is a quality of life issue," Broadbent expalins. For the public, the issue of landscaped medians and the appearance of the barriers designed to prevent crossover accidents is important. On freeways where a barrier is proposed, the look of the barrier routinely becomes a major topic of discussion between the public and Caltrans project staff.

Technical experts and maintenance crews counter that the integrity of the barrier is easier to maintain, reducing exposure of maintenanace cres to live traffic while making repairs.

The Office of Landscape Architecture, as part of the department's Context Sensitve Solutions initiative, initiated a study of highway barrier aesthetis in 2001 to see if it could find common ground in these conflicting viewpoints. "What we found is that everyone shared the goads of improving safety and enhancing the environment. The challenge was how to get there. We are trying to give project designers more flexibility and tools in determining the best median barrier alternative from both engineering and aestheic quality standpoints," says Keith Robinson, Chief of the Office of Landscape Architecture. California has been the national leader in this area, serving as a driving force in a nationwide examination of aesthetic bridge rails and barriers. Caltrans'

Roadside Safety Technology Branch conducted a $434,000 study of different types of textured barriers. From the study, a set of guidelines was produced allowing designers to develop a variety of crashworthy textures. Further, Caltrans is participating in a $600,000 federal program to produce new barrier textures and bridge rail designs.

A smooth concrete barrier has been a staple in Caltrans design arsenal for decades.

"The smooth barrier is strong and functional," says Rich Peter, Chief of the Caltrans Roadside Safety Technology Branch, the unit responsible for crash-testing barrier walls. "But beauty is in the eye of the beholder and some people may not see the natural beauty in a smooth concrete barrier wall."

Robinson says the initial challenge was to get the various parties to consider alternatives to their long-held positions. "For example, Caltrans maintenance prefers concrete because it requires less maintenance. That means that our maintenance people do not have to be out repairing the concrete with life traffic just a couple of meters away," Robinson explains. "Many of our local partners do not like concrete because it is not aesthetically pleasin. They both have legitimate concerns."

The highway barrier aesthetics study focused on three main areas: safety, constructability and maintainability. Various design ideas were developed and crash-tested by the department at the Caltrans Dynamic Test Facility in West Sacramento.

"We had to assure ourselves, first and foremost, that by treating the concrete with a textre or other material, we did not create a situation that could cause a potential safety problem," Broadbent says.

Caltrans researchers tested a number of alternative textures and patterns on the face of a Type 60 concrete barrier, which is 1.6 m tall (including a built-in-glare screen and 600 mm wide at the base).

"The successfully tested textured barrier behaved similarly, but bot identically to smooth concrete. The barriers, when crash-tested, were proven to be safe and met the design criteria we demanded," Peter says. "However, a car running into a textured barrier face could sustain more damage from a smooth barrier because of the natural friction in the texture."

With the safety issue resolved, Caltrans researchers turned to constructability and maintainability of the textured barrier. Crews from MBI Construciton in Livermore demonstrated a new method of constructing slip-formed, textured concrete barrier pioneered by Mike Allen of Allen and Sons Construction.

At the MBI construction yard in Lodi, the company poured a30 m-long barrier and rolled on a dry-stacked rock design into the wet concrete.

The pattern for this design is made of urethane and is attached to a roller. As the concrete is poured, the rollers on the back of the slip-form machine are pressed against the wet concrete like a rolling pin over dough.

Designs that cover the gamut from simulated stone to a beach scene including sun, surf and sand can be imprinted into the concrete.

"Concrete is a material that is pliable and flexible up until the time it dries. It really has tremendous potential in terms of architectural a aesthetic character," Broadbent says. Armed with this study, the project designers can come up with solutions that meet the engineering criteria, look good and enjoy the support of the public."

Guidelines to implement the study's alternatives for textured concrete barriers are being reviewed by Caltrans engineering manangement and are expected to be issued before the end of the year.

The department also has evaluated and approved other aesthetic barrier designs. These include steel-backed timer rails and a stone-cast barrier consisting of precast concrete elements covered with real stone.

The first planned location to receive one of these environmentally friendly barriers is the section of Highway 163 through San Diego's Balboa Park. The 5 km-long sectoion of highway slices through the park. The median is 16.8 m wide and is heavily wooded. Last year Caltrans Distric 11 engineers responding to a series of accidents proposed installation of a median barrier. "The public was not happy with the concrete alternative. They supported the effort to improve safety, but were very vocal in their opposition to something that detracted from the beauty of the park," says District 11 Director Pedro Orso-Delgado.