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Highways for LIFE

Arrow North Dakota Demonstration Project: Whitetopping on U.S. 2 West of Rugby

Project Overview and Lessons Learned

Project Overview

U.S. 2 between Rugby and Berwick, ND, is a four-lane divided highway that serves as a vital interregional east-west route linking the northern portion of the State. In the westbound direction, the original hot-mix asphalt (HMA) pavement surface was in increasingly poor condition because traffic and harsh seasonal weather caused distresses to increase beyond the budget of normal maintenance efforts. Rutting, fatigue cracking, and severe transverse and longitudinal cracking made this section of U.S. 2 not only rough, but also unsafe for the traveling public.

Whitetopping offered NDDOT a cost-effective rehabilitation alternative to restore ride quality in the westbound lanes while leaving the existing deteriorated HMA pavement in place as a sublayer. Bonding between the original pavement and the new 7-inch (in) thick portland cement concrete (PCC) whitetopping optimizes the material properties and eliminates the need for dowel bars and tie bars that would be required in conventional concrete pavement. Not using steel reduces the initial project cost, increases construction speed, and simplifies any future repairs. 

The U.S. 2 divided highway alignment presented a perfect opportunity to use full lane closure by shifting traffic onto the two open eastbound lanes, removing traffic from the work zone and enhancing worker and public safety during paving operations.

HfL Performance Goals

Safety, construction congestion, quality, and user satisfaction data were collected before, during, and after construction to demonstrate that whitetopping and total lane closure can be used to achieve the HfL performance goals in these areas.

  • Safety
    • Work zone safety during construction—At the completion of construction, no motorist crashes were reported at the project location. The speed of construction and detouring traffic away from the construction zone played a key role in meeting the goal of keeping the crash rate well below historical levels for this segment of the highway. It is anticipated that 3-year average crash rates will meet the HfL criteria of 20 percent reduction because of the improved riding surface and new safety features, such as turn lanes and updated shoulder slopes.
    • Worker safety during construction—No worker injuries occurred during construction, which exceeded the goal of less than a 4.0 rating on the OSHA 300 form. Worker safety was greatly increased by using full lane closure to eliminate live traffic from the work zone.
  • Construction Congestion
    • Faster construction—Full closure of the U.S. 2 westbound lanes allowed the contractor to pave both lanes at the same time rather than in two passes. This helped reduce paving construction time by 36 percent. Under conventional construction, the impact on both road directions from construction-related congestion was estimated at 53 days. Paving both westbound lanes in a single pass with whitetopping and the use of full lane closure reduced pavement construction to only 34 days. While not meeting the HfL goal of 50 percent reduction in the time highway users are impacted, the innovations made a substantial reduction toward this goal compared with traditional methods.
    • Trip time—For safety, the speed limit was reduced by 10 miles per hour (mi/h) (16 kilometers per hour (km/h)) for head-to-head traffic on the original eastbound lanes, causing a 16 percent increase in trip time. Traditional phased construction would have reduced the speed limit even more (under traditional methods one westbound lane of traffic would have been maintained at 40 mph (64 km/h) and then 25mph (40 km/h) near the immediate work area), causing a greater increase in trip time.
    • Queue length during construction—Even though the trip time was increased from one end of the project to the other, no noticeable backups occurred, keeping moving queue lengths well below the HfL criteria of 0.5 mi.
  • Quality
    • Smoothness and noise— Quality was measured in terms of smoothness and noise both before and after construction. The field data document a 64 percent drop in post-construction IRI value, a considerable increase in smoothness. Pre-construction IRI was 199 inches per mile for the existing HMA pavement, while post-construction IRI was only 71 inches per mile, which fails to meet the HfL target value of 48 inches per mile but is still a vast improvement over the original pavement.
    • Noise—The sound intensity level went from 102.8 dB(A) to103.9 dB(A). Typically, newly constructed longitudinally tined concrete pavements have a noise intensity range from 102.0 to 105.0 dB(A), depending on the type of texture used in combination with the tining. Therefore, while the HfL goal of 96.0 dB(A) was not met, the noise level of the new pavement is reasonable.
    • User satisfaction—Post-construction survey results show that local communities were very accepting of the full lane closure concept, which kept traffic flowing freely and the public away from construction dust and debris. Public satisfaction is very high with the finished product and meets the HfL user satisfaction criteria.

Economic Analysis

The benefits and costs of this innovative project were compared with those of a similar resurfacing project with a more traditional delivery method. The result of a life cycle cost analysis indicates that NDDOT's approach is similar in cost over the life of the pavement to conventional overlay methods. The actual savings were realized by minimizing the number of construction days, saving $32,927 in user delay costs during construction.

Lessons Learned

With this project, NDDOT achieved a better understanding of the whitetopping method. Until now, whitetopping was not considered for major highway rehabilitation largely because of lack of local experience. This was the first major whitetopping project in North Dakota, and it was successful in demonstrating the constructability of whitetopping and enlightening designers and contractors alike on the viability of this innovative rehabilitation method.

The contractor on this project was able to use the milled HMA pavement as a stable haul road to supply fresh concrete to the paver. This is not always the case on whitetopping or any overlay project in which the original pavement is severely distressed and milling reduces the structural capacity of the pavement. NDDOT had originally specified that no traffic be permitted on the milled HMA pavement, but allowed the contractor access after no damage by haul trucks was observed.

During the first few days of paving, the contractor was extra diligent in timing sawcutting operations because of the possibility of shrinkage stress from large temperature swings during the late-season paving schedule. Some relief cuts were made to prevent uncontrolled cracking early in the paving schedule until curing rates were fully understood. After the first few days of paving, the contractor was more comfortable with the operation and was able to increase production. Also, the lack of steel reinforcing made production more efficient by eliminating the time required to set dowel baskets, as traditional concrete paving methods require.

Conclusions

The North Dakota whitetopping project on U.S. 2 exemplifies the Highways for LIFE principles. Paving construction time was cut by 36 percent compared with traditional paving operations, while a high level of safety was maintained for workers and the traveling public. Crashes are expected to be lower over the project's service life because of design features and a durable pavement surface. The whitetopping and full lane closure innovations were major contributing factors in reducing the overall project cost. The postconstruction smoothness level, while not meeting the HfL goal, is a vast improvement over the smoothness level of the original pavement. The noise level after construction also does not meet the target value, but is within the range for similar textured pavements. Overall, the end users of the new roadway are very satisfied with the finished product.

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Contact

Mary Huie
Highways for LIFE
202-366-3039
mary.huie@dot.gov

Updated: 06/06/2011

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United States Department of Transportation - Federal Highway Administration