Project Overview and Lessons Learned

Project Overview

Minnesota’s TH 36 is a major east-west, four-lane urban highway connecting the suburb of North St. Paul to the downtown areas of St. Paul and Minneapolis. The project encompasses about 2.2 mi (3.5 km) of TH 36 through North St. Paul from White Bear Avenue to TH 120 (Century Avenue). Several retail businesses line this corridor, as well as a popular recreation trial and a high school.

The project design addressed two key needs: 1) improving safety for highway users and pedestrians and 2) improving travel efficiency through the corridor. The major design feature was the construction of overpasses to separate crossroad and pedestrian traffic from TH 36, which eliminated inefficient and hazardous intersections.

Traditional staged construction methods would have impacted traffic on TH 36 for an estimated 19 months for a project of this scope. Mn/DOT’s decision to use both contracting and construction innovations reduced the impact on TH 36 traffic to 6.5 months. Speed of construction, user and worker safety, and quality were enhanced by incorporating innovations throughout the project:

• Full closure of TH 36. Full closure of a major urban freeway is a new concept to Mn/DOT and in the past was reserved for low-volume roads. Including full closure in this project helped Mn/DOT evaluate the cost, time savings, motorist and worker safety benefits, and quality of and public reaction to this innovative approach compared to multiyear staged construction.
• Intelligent compaction equipment. Intelligent compaction rollers and lightweight deflectometers were used on the project to improve the quality of grading operations. Theses rollers allow operators to monitor embankment and paving material compaction in real time and make adjustments as needed. This project was the first time Mn/DOT used intelligent compaction and lightweight deflectometer acceptance testing in lieu of test rolling and sand cone density testing.
• Locked incentive date. An LID specified in the contract would not allow extensions to the contract date and eliminated the possibility of claims. This served as an incentive for the contractor to complete the project early.
• A+B contract bidding. A+B (cost-plus-time) contract bidding was used to reduce contracting time.
• Lane rental. A rental fee was imposed if a lane on TH 36 needed to be closed before or after the full closure to accommodate maintenance or cleanup operations. Lane rental fees helped ensure minimal impacts on motorists.
• Intelligent transportation system. This system allowed Mn/DOT to monitor traffic on the detour routes around the construction.

Full closure was the highlighted innovation on this project and the focus of Mn/DOT’s in-house market research team. The team's efforts to capture the DOT’s and public’s experience with full closure will benefit future projects of similar scope.  

HfL Performance Goals

Safety, construction congestion, quality, and user satisfaction data were collected before, during, or after construction to demonstrate that innovations can be deployed while simultaneously meeting the HfL performance goals in these areas.

• Work zone safety during construction—No motorist incidents occurred in the TH 36 construction zone. The full closure eliminated through traffic and any possibility of traffic-related incidents in the work zone.
• Worker safety during construction—No worker injuries were reported, which exceeded the HfL goal for worker injuries of less than 4.0, based on incidents reported by the contractor via OSHA Form 300.
• Facility safety after construction—Reported injuries and fatalities for the first year after construction were down 40 percent compared to the 3-year average before the project started. This trend is likely to continue because six at-grade intersections were removed from the TH 36 corridor, making it a safer throughway.

• Construction Congestion
  • Faster construction—Traditional construction methods using partial roadway closures to reconstruct TH 36 coupled with traditional contracting methods would have impacted traffic for an estimated 19 months. The full closure and innovative contracting methods allowed the contractor to reopen all lanes of TH 36 in only 6.5 months and exceeded the goal of 50 percent reduction in traffic impact.
  • Trip time—Measurement of trip time is a valuable tool to evaluate the impact of construction on motorists traveling through the work zone. While trip time measurement applies to other HfL projects, full closure prevented the use of this technique.
  • Queue length during construction—Full closure necessitated moving traffic onto detour routes, which eliminated queue lengths associated with lane reduction and traffic interruptions from conventional partial roadway closures.
• Quality
  • Smoothness and noise—The tire-pavement noise and smoothness quality indicators measured for the highway were slightly higher than the goals set for the HfL program. Specifically, the noise level was 1.0 dB(A) higher than the goal of 96 dB(A) and the smoothness was 2 inches per mile higher than the goal of 48 inches per mile.
  • User satisfaction—Mn/DOT sponsored a comprehensive evaluation of the public’s assessment of the project. Survey results of area businesses, residents, and commuters indicate an overwhelming approval of the way the project was executed, exceeding the goal of achieving 80 percent or greater satisfaction with the methods used to keep traffic disruption to a minimum during construction. Construction speed was cited as the top reason for satisfaction. The study did not directly address user satisfaction with the new facility compared with its previous condition. However, nearly half of those surveyed indicated there was nothing the DOT could have done better, suggesting that overall satisfaction with the newly reconstructed corridor was high.

Economic Analysis

The costs and benefits of this innovative project approach were compared with building the project under more traditional methods. The cost assumptions for the traditional approach were determined from discussions with Mn/DOT staff and national literature.

The economic analysis revealed that Mn/DOT’s innovative approach increased project costs by about $2.1 million, or 7 percent, compared to conventional construction practices. User cost associated with detouring traffic to alternate routes during the full closure exceeded the savings in construction costs.

Lessons Learned

The project was a success in terms of safety, cost, and traffic impact on TH 36. Several firsts occurred on this project and many lessons were learned with the use of new methods. The University of Minnesota undertook a multiple task study to document the experience gained from this full closure project. The following are among the lessons learned:

• It is important to predetermine detour routes well in advance of the project and make necessary improvements to detour pavements to handle increased traffic volume during the project.
• Surrounding signalized intersections and those directly affected by the detours should be observed for backups and congestion. Based on observations, signal timing was adjusted to accommodate the change in traffic brought on by the full closure.
• Part of the success of routing the traffic around the full closure resulted from Mn/DOT's effort to work closely with county and city engineers to assemble a comprehensive traffic plan.
• Good weather played a role in the success of the full closure. The weather for the construction season was relatively good and rain affected production for only a couple of days. Heavy rains lasting several days could have slowed grading operations considerably and negatively affected the ability of the contractor to complete the full closure on time.
• The decision to use full closure or even consider it as a construction method option should be made early in the design process to allow for a complete analysis of the benefits. The decision to use full closure on the TH 36 project occurred late in the design process as a method to reduce construction cost by reducing construction time. Additional time would also provide designers with more opportunities to educate the public on the advantages of completely closing a roadway for reconstruction.
• Closing the roadway should begin on a Tuesday rather than a Monday (as was the case for this project) so the posted information on alternate travel routes is fresh in the minds of motorists driving through the project area the day before the closure. 

Conclusions

¹ University of Minnesota. August 2009. TH 36 Full Closure Construction: Evaluation of Traffic Operations Alternatives, Task 8 Deliverable: Lessons Learned from the TH 36 Full Closure Construction Project.