U.S. Department of Transportation
Federal Highway Administration
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Federal Highway Administration Research and Technology
Coordinating, Developing, and Delivering Highway Transportation Innovations
This magazine is an archived publication and may contain dated technical, contact, and link information.
|Publication Number: FHWA-HRT-07-002 Date: Jan/Feb 2007|
Publication Number: FHWA-HRT-07-002
Issue No: Vol. 70 No. 4
Date: Jan/Feb 2007
California moved forward with accelerated construction and experienced less traffic disruption.
|(Above) Innovative construction methods enabled Caltrans to cut the I-15 Devore project from 10 months to 19 days. At the center of this photo, a transformer adjusts a moveable barrier to optimize traffic flow around construction with a dynamic lane configuration.|
Transportation trends in the United States may be converging to form a "perfect storm" 1 for departments of transportation and the public. Few new roadways are being built, and congestion is increasing. Existing roads require more repairs, further disrupting traffic and leading to public displeasure at work zone-related travel delays. These trends only stand to become worse unless the transportation community can craft innovative solutions, such as accelerating urban freeway reconstructions.
According to The 2005 Urban Mobility Report by the Texas Transportation Institute, from 1982 to 2000 the number of urban areas in the United States with more than 20 hours of annual delay per peak-hour traveler grew from 5 in 1982 to 51 in 2003, caused in part by work zones. During the 2001 peak roadwork season, for example, there were an estimated 3,110 construction work zones on the National Highway System. In the Federal Highway Administration's (FHWA's) Moving Ahead: The American Public Speaks on Roadways and Transportation Communities, 32 percent of survey respondents expressed dissatisfaction with work zones.
As with other States, California is searching for a way to address the problems caused by the converging trends of more congestion, lower budgets, and roads in need of repair. The California Department of Transportation (Caltrans), which oversees a State highway system of 78,000 lane-kilometers (km) (48,467 lane-miles), is achieving some success through its Long-Life Pavement Rehabilitation Strategies (LLPRS) program. The program, initiated in 1998, addresses California's need for cost-effective practices in rebuilding the aging pavements in its urban highway network. The goal is to rebuild approximately 2,800 lane-km (1,740 lane-miles) of high-volume urban freeway with pavements that are designed to last more than 30 years.
In 2004, Caltrans applied an innovative, fast-track reconstruction program to a heavily traveled LLPRS project on I-15 in the city of Devore in southern California. A 4.5-km (2.8-mile) stretch of badly damaged concrete lanes was rebuilt in only two single-roadbed continuous closures (also called "extended closures") totaling 210 hours, using counterflow traffic (opposite direction to the main traffic flow) and 24-hour-per-day construction operations. Traditional nighttime-only closures would have required 10 months' work, as estimated on the preconstruction schedule. Instead, the rebuilding took 19 days, with each extended closure for one roadbed lasting 9.5 days.
|I-15 Project and Nearby Highway Network|
Other innovations adopted for this I-15 Rapid Rehabilitation (Rapid Rehab) project included:
Project engineers used analysis software, which incorporates traffic simulation models, to arrive at an optimal and economical scenario for rehabilitation closures, a construction schedule, and a traffic management plan. The postconstruction data validated the preconstruction analysis and simulation estimates of productivity and traffic delays.
"The [software] model enabled our project engineers to optimize the balance between construction schedule, traffic delay, and agency cost," says Larry Orcutt, director of Caltrans's Division of Research and Innovation. "We were further impressed when we found that our postconstruction data validated the predictions made by [the software]."
The public outreach resulted in a 20-percent reduction in traffic demand through the construction work zone. The maximum peak-hour delay was cut in half, from the expected 90 minutes to 45 minutes. Surveys taken on the project's Web site showed that public perception of the Rapid Rehab approach shifted dramatically; initial reluctance and objections changed to expressions of support.
"Two months prior to the first roadbed closure, the department had a 1-month hiatus to resequence the approach and staging of the proposed Rapid Rehab work," says Hector Davila, deputy district director for Caltrans District 8 Construction Division. The advantages of accelerated reconstruction resulted in significant benefits, including a 30-year pavement life expectancy and a 25-percent reduction in construction costs.
"We saw no downside from this Rapid Rehab project," Orcutt says. "Traffic disruptions were dramatically shorter, and we spent about $6 million less than we would have if we had used the traditional method with repeated nighttime traffic closures. Not only that, we also found that both worker and motorist safety were improved."
Closure Options for I-15 Devore Project
|Closure Scenario||Schedule Comparison||Traffic Delay||Cost Comparison|
|Number of Closures||Closures (Hours)||Road User Cost ($M)||Maximum Delay (Minutes)||Agency Cost ($M)||Total Cost ($M) to Users & Agency|
The most economical closure scenario was selected based on the analysis software's estimates from the perspective of closures, schedule, traffic delay, and total cost.
The Devore corridor of I-15 experiences consistently high weekday commuter peaks, including heavy truck traffic, and an even higher volume of 120,000 average daily traffic on weekends when leisure travelers in the Los Angeles area drive to and from Las Vegas and resort locations along the Colorado River. The project scope called for replacing severely deteriorated concrete slabs and base pavements with a new cross section of 29-centimeter (cm) (11.4-inch) doweled slabs using rapid-strength concrete (Type III) and a 15-cm (5.9-inch) asphalt concrete base of rich bottom (AR-8000) mix on top of the remaining aggregate base or native material.
Progressive Staging Construction and Dynamic Lane Closures
|Work on the I-15 project was divided into two segments. While rehabilitation proceeded on the northbound lanes, the southbound lanes were turned over to two-way traffic, with the moveable barrier shifting one lane in the morning and afternoon to accommodate traffic flow.|
The preconstruction analysis sought the most economical reconstruction closure scenario while integrating the competing concerns of construction schedule, traffic impact, and agency cost. Four closure scenarios were compared: 72-hour weekday, 55-hour weekend, one-roadbed continuous (24 hours per day, 7 days per week), and 10-hour nighttime. The analysis concluded that the continuous/extended closure scenario would be the most economical.
Compared with traditional 10-hour nighttime closures, the preconstruction analysis indicated that the extended closure scenario would present about 80 percent less total closure time, about 30 percent less road-user cost due to traffic delay, and about 25 percent less agency cost for construction and traffic control.
The result? The I-15 northbound roadbed was closed for reconstruction, and northbound traffic was switched to the southbound side via median crossovers at the ends of the work zone. Traffic in the two directions shared the southbound lanes as counterflow traffic separated by the moveable barrier. The same process was repeated for reconstruction of the southbound roadbed.
For pavement design and material alternatives, Caltrans used the software model to make comparisons from the perspectives of production scheduling and traffic inconvenience. As a result, Caltrans selected: (1) rapid-strength concrete with a 12-hour curing time rather than fast-setting hydraulic cement concrete with a 4-hour curing time; (2) a 15-cm (6-inch) new AC base, rather than a 15-cm lean concrete base; and (3) a widened 4.3-meter (14-foot)-wide lane, rather than the usual 3.7-meter (12-foot)-wide lane tied to a new concrete shoulder on the outermost truck lane.
High project bids in the first round of construction bidding resulted in altering the rehabilitation scope. The initial scope included reconstruction of two (outermost and adjacent) lanes, but the revised project included reconstruction of only the outermost lane and targeted partial (about 10 percent) slab replacement on the adjacent lane. Moving the project from spring to fall 2004 resulted in a significant 5-percent increase in traffic volume. Consequently, the road-user cost was estimated to increase by 90 percent, from $5 million to $9.5 million, and the estimate of maximum peak-hour queue delay increased from 75 to 90 minutes.
The I-15 project combined conventional construction materials and operations with state-of-the-practice technologies to expedite construction and minimize traffic impacts. Additional project features that contributed to traffic control included the following:
Use of the moveable barriers, at a cost of about $1.5 million, helped to balance traffic impacts to commuters and weekend travelers by providing dynamic lane configuration. In twice-daily operations that required only 30 minutes to complete, each barrier was moved to convert one additional lane temporarily from the rehabilitated asphalt concrete shoulder to accommodate peak directional commute traffic.
The Devore Project is the first implementation of an automated information system in work zones for this type of project in California. "Prior to construction, it was decided to have a 24-hour command center," Davila says. "You could practically run the entire project from this center. There were several monitors displaying the real-time data that were being shown to the public, and camera controls were available to view all the ongoing construction work and traffic flow as it was occurring."
The system provided motorists with real-time information on travel and detour routes. The travel information was posted on permanent and temporary changeable message signs strategically placed at key decision points for roadway users. The information also was posted on a traffic roadmap on the project Web site as part of an interactive public outreach campaign.
Convincing motorists to use alternate routes or adjust their commuting modes to avoid traffic disruption during construction was key to the project's success. Prior to construction, large employers and affected businesses (airports, postal and package-service companies, for example) were informed through project fliers, public meetings, and intensive media outreach. Project planners hoped that the dynamic effort to raise public awareness could prompt a 20-percent reduction in peak-hour traffic demand, but they acknowledged the challenges of targeting daily commuters, the uniqueness of the I-15 Devore corridor, and lack of detour routes close to the construction work zone.
To reduce traffic, Caltrans implemented a media campaign, an outreach program that included public meetings in local communities, a project information Web site, and a project information telephone hotline. Printed materials, including a comprehensive project brochure and construction flyers, were distributed. E-mail contact included a construction advisory electronic bulletin and a "fast-fax" system for project alerts. All these efforts focused on informing the public about the project and providing area travelers with the information required either to divert to alternate routes around the work zones or to time their trips to coincide with construction schedules.
"Our massive public outreach campaign and available data are what made this project a success," Davila says.
|Automated Work Zone Information Systems|
Three months before construction started in October 2004, the project Web site was initiated to provide up-to-date, comprehensive project information. The "I-15 Devore Rapid Rehab Project" Web site appeared as the first headline on the Caltrans District 8 homepage, which linked to the Web sites of neighboring local agencies and the surrounding three Caltrans district offices in southern California. The site was updated regularly with up-to-the-minute information on construction progress, traffic control plans, detour routes, real-time travel information, press releases and fast-faxes for project updates, and community Web surveys.
The surveys enabled Caltrans to determine changes in public perception to the Rapid Rehab theme. In the 5 months preceding the extended closures and while the closures lasted, the project Web site received nearly 100,000 hits and played an important role as an interactive tool to gain input from the public. Community Web surveys indicated that the majority (72 percent) of the people who used the site considered the project information it provided useful to their trip planning.
"We even provided live streaming video of current traffic conditions through the project limits," says Davila. "Traveling motorists were able to log on to our Web site before their trip departure, view traffic conditions, and then decide whether they would drive through the project, take alternate routes, or wait until traffic cleared up."
According to a Caltrans's study of the construction, the contractor's production rates reflected a significant learning curve. The majority of operations during the southbound re--construction, which took place later in the project, showed a 28-percent increase in speed of slab removal and 22-percent faster paving than during the northbound reconstruction. The observed learning-curve effect is attributed to better management by the contractor in the second closure and to the contractor's devotion to meeting the scheduled completion date to avoid the late-opening penalty in the incentive/disincentive provisions of the contract.
|The round-the-clock nature of the project and various innovative aspects enabled its four major components to proceed smoothly.|
The continuous lane reconstruction on the outer truck lane exhibited twice the productivity of the random-slab replacement operation on the inner truck lane. For example, slab removal during the continuous-lane reconstruction operation on the southbound construction resulted in more than twice the productivity of the random-slab removal (90 meters/hour versus 37 meters/hour). The lower productivity of random-slab paving for both slab removal and paving was due to these operations requiring extra time for mobilization and demobilization.
Two critical traffic management goals were met: Overall traffic volume through the work zones was 20 percent less and the maximum peak-hour delay was 50 percent less than projected. Although 90-minute delays were predicted originally for the extended closures in the preconstruction analysis, the maximum peak delay was measured at 45 minutes on weekdays (southbound).
Traffic demand through the work zones was greatly reduced by diversions to major freeway detour routes. Eastbound I-10 was used as the northbound I-15 detour; the replacement showed a 10-percent daily traffic volume increase, with a high of 36 percent during morning peak hours. Southbound I-215 was used as the southbound I-15 detour; it received a daily volume increase of about 15 percent.
Before- and after- construction surveys on the project's Web site showed a dramatic change in public perception of the accelerated freeway reconstruction project. Most respondents showed strong initial aversion to the extended closures, with 64 percent of the preconstruction surveys expressing a preference for traditional nighttime or weekend closures and 14 percent requesting complete cancellation of the project. Preconstruction survey results also revealed that the public was not initially predisposed to altering its travel patterns and modes to avoid the delays anticipated in the work zones.
However, public perception of the project changed substantially as travelers were able to compare their initial expectations against their actual experiences. Provided with construction schedule information and traffic delay forecasts, a significant percentage of commuters reported changing daily commuting modes and travel routes during the extended closures.
Seventy percent of the respondents to the postconstruction survey expressed support for Rapid Rehab projects, indicating that the California public is willing to bear increased traffic delays for a short period in exchange for compressed construction schedules.
A traffic monitoring study comparing traffic conditions before and during construction showed that the preconstruction goal of a 20-percent reduction in traffic demand through the work zones during peak hours was achieved, as noted in the previous section, through a combination of "no-shows," diversions, and travel mode changes. Although the preconstruction survey showed that 61 percent of respondents said they would not change their travel patterns even if the I-15 corridor were congested during the construction, only 24 percent of respondents to the during- and after-construction surveys indicated they had not changed their travel plans. Forty percent of respondents reported that they adjusted their departure times based on information obtained through Caltrans's outreach, and 32 percent reported taking detours during the extended closures.
The main contributor to this change in public perception from negative to positive was the comprehensive public outreach program. "This changed the public perception dramatically," Davila underscores.
The I-15 Devore Project team was honored with two Caltrans 2005 Excellence in Transportation Awards, one for public awareness and the other for innovation.
|Anticipated and Actual Travel Mode Changes Due to I-15 Project|
Eul-Bum Lee is an associate researcher at the Institute of Transportation Studies at the University of California, Berkeley. He earned M.E. and Ph.D. degrees at U.C. Berkeley.
David K. Thomas is an engineering manager for the Parsons Brinckerhoff engineering firm.
1 Refers to the 1991 Nor'easter storm, where several severe circumstances converged to cause a catastrophic event off the northern Atlantic coast.
Portions of this article are excerpts from "'Rapid Rehab' Accelerated Urban Highway Reconstruction: I-15 Devore Project Experience."