Earlier this year, for example, Illinois Tollway engineers researched the possibility of including relatively new cable median guard-rail systems on roadway projects already in the advanced planning stages and scheduled for completion in 2005. The tollway felt these protective barriers would be valuable safety enhancements to prevent vehicle crossover incidents.
It also recognized, however, that incorporating these systems into the projects on such a tight deadline would not be easy. Manufacturers had to be selected through a competitive bidding process, and the engineering challenges would require timely collaboration between multiple parties. Plus, the new cable guard-rail systems had to be completely installed on 70 miles of road during one construction season, which in the Midwest can be delayed or cut short by inclement weather.
The tollway, however, would not be deterred. By working closely with its design engineer, Wight & Co., Darien, Ill., it overcame these obstacles and still finished both projects on time and under budget. Following are the details and highlights of how the tollway and its contractors added an important safety feature to the I-88 and I-90 toll roads that will prevent crossover accidents and save lives.
High tension
The Illinois Tollway is a 274-mile system that includes the Ronald Reagan Memorial Tollway (I-88), the North-South Tollway (I-355), the Northwest Tollway (I-90) and the Tri-State Tollway (I-94, I-294, I-80/I-294) and serves 1.4 million vehicles daily in 12 counties in northern Illinois. The vast majority of these roads are in a 50-mile radius surrounding Chicago.
Under the leadership of Executive Director Jack Hartman, the Illinois Tollway has been aggressive in its efforts to make the system safer and reduce travel times. In September 2004, the Illinois Tollway board of directors unanimously approved Gov. Rod Blagojevich’s $5.3 Congestion-Relief Plan, “Open Roads for a Faster Future.” This 10-year plan will enable the tollway to rebuild or restore 90% of the system, including the western portions of I-88 and I-90. In studying the latest technical literature, tollway engineers decided that these tollway segments were ideally suited to taking advantage of advances in cable barrier technology.
Cable systems have been used as a roadside barrier since the 1960s. By the 1980s, some states, including Missouri, began using a modified cable rail as a median barrier, which offered several benefits over traditional steel or concrete barriers. Most importantly, the cable barriers were a more forgiving system in that they reduced deflection, increasing the chances that the occupants of errant vehicles would walk away from accidents uninjured. These systems also were considerably less expensive and bidirectional, meaning one cable would protect both sides of traffic. Also, cable barrier installed in existing medians usually require minimal site work.
Despite these advantages, most states and tollways have been slow to adopt the generic roadside cable systems, in part because of the perception of high maintenance costs. In recent years, some manufacturers have developed proprietary, high-tension designs for cable median barriers with stronger breaking loads and greater elasticity, thus limiting deflection and damage to a short area of fence near the point of impact. Fewer posts are damaged in a hit, and repairs can be quickly made with just hand tools. Also, the high-tension wires could withstand multiple hits without having to be replaced.
The high-tension cable systems are beginning to gain wider usage throughout the U.S as retrofit barriers, usually in spot locations where crossovers are most prevalent. They are especially easy to install in wide, flat medians such as the Illinois Tollway’s I-88 and I-90 segments. Given the time constraints, however, the selection and installation of the two systems could not be accomplished without modifying aspects of the project delivery methodology.
Nonprescription for success
After the tollway decided to add the cable barriers to the two projects, one of its first steps was to collaborate with Wight & Co. in selecting the manufacturer. Its goal was to give the handful of companies that made such systems an equal chance to win the assignment. To ensure product quality and minimize costs, the tollway and Wight quickly developed generic performance specifications (based largely on the commonalities in the manufacturers’ proprietary specifications) that would meet or exceed NCHRP Test Level 3 safety standards.
Internally, the tollway project manager put together an ad hoc team of personnel from its maintenance and materials departments and its general engineering consultant. The group tapped into resources from other states that had installed these cable systems such as Ohio, Oklahoma, North Carolina and Utah. Participants became familiar with the project details and were able to add their input and ideas in real-time. This process virtually eliminated the long delays caused by the traditional project management methodology of getting approvals one department at a time. Consequently, the development of the performance specifications—typically a four- to six-month process—was completed in less than a month.
This kind of flexibility was a hallmark of the entire project. Wight & Co. developed preliminary drawings of the cable systems’ geometry and layout, which the general contractor, GF Structures, adapted based on its knowledge of the location and input from the manufacturer and other experts. For example, the tollway initially thought the cable system would have to terminate at each of the 13 bridges on I-88, but GF Structures suggested running the cables around the bridges. Also, the tollway wanted to use socketed sleeves with a concrete foundation for the I-90 cable system, but the contractor presented convincing data showing that driving the posts into the ground would be more cost-effective.
By not being prescriptive in its specifications, the tollway gave its contractors the freedom to find innovative, cost-saving alternatives that would perform just as well.
This collaborative approach proved invaluable in resolving numerous and multifaceted engineering challenges. Where would the systems be placed in the median? What was the optimal distance between the posts? Should the barriers be broken into segments to accommodate turnarounds by police and maintenance vehicles? How would the proposed solutions to these challenges affect drainage, maintenance, pier protection and snow removal? What were the tollway’s inventory needs in terms of spare parts and equipment?
As each issue arose, appropriate members of the tollway staff and contractors would voice their opinions and concerns and quickly reach consensus on a course of action.
On the grassy median
The Illinois Tollway’s installation of new high-tension cable guard-rail systems across nearly 70 miles of median will be completed by the end of 2005. It is one of the first in the country with such extended length systems, and the tollway has adopted the policy of installing these systems wherever it has a grassy median.
As more states adopt increasingly conservative warrants for median barriers, agencies need to be aware of their options regarding low-cost, high-tension cable guard-rail systems. Whenever feasible, they also should consider installing such systems as an add-on to existing or planned rebuilding projects.
A slow and cumbersome bureaucratic system can be the biggest barrier to adopting innovations in highway safety engineering. The two Illinois Tollway projects demonstrate that when an agency is fully committed to getting the job done it will find creative ways to surmount any and all hurdles. By moving quickly to take advantage of its capital improvement budget and collaborating with progressive, responsive staff and contractors, the tollway was able to better serve its customers with safety enhancements that would be in place in time for the 2005-06 winter driving season.
