|FHWA > HfL > Rhode Island Demonstration Project: Replacement of Frenchtown Brook Bridge No. 435 > Data Acquisition and Analysis|
Rhode Island Demonstration Project: Replacement of Frenchtown Brook Bridge No. 435
Data Acquisition and Analysis
Data on safety, traffic flow, and quality before, during, and after construction were collected to determine if this project met the HfL performance goals. The primary objective of acquiring these types of data was to quantify project performance to provide an objective basis to determine the feasibility of the project innovations and demonstrate that the innovations can be used to do the following:
This section discusses how well the RIDOT project met the HfL performance goals related to these areas.
The project included the HfL performance goal of achieving a work zone crash rate equal to or less than the existing conditions. During this project, no crashes occurred, satisfying the HfL goal. Work zone safety was ensured by completely closing the bridge to traffic, accelerating construction, and using prefabricated bridge components. Accelerated construction methods, including the use of prefabricated bridge components, made the brief traffic detour feasible.
The project included the performance goal of achieving an incident rate for worker injuries of less than 4.0 based on the OSHA 300 rate. Not only did closing the bridge to traffic help achieve this goal, but precasting the bridge system at an approved facility eliminated the need for workers to spend most of their time exposed to falling hazards, which would have been required with traditional cast-in-place construction methods. No work-related injuries occurred during construction, resulting in an OSHA Form 300 score of 0.
The safety of the traveling public was of concern. ADOT’s foremost solution was to minimize traffic disruption and interaction with construction activities and workers. The crash history for the 5-year period between May 1, 1998, and April 30, 2003, showed a total of 245 crashes, 134 of which were rear-end crashes. The crash breakdown was as follows: 77 percent noninjury, 11 percent possible injury, 9 percent nonincapacitating, 1 percent incapacitating, zero fatal, and 2 percent unknown.
It is difficult to compare crash data before and after construction at this site because both the traffic volume and flow have changed. Davisville Road under the relocated Route 403 project, a major undertaking of RIDOT of which this project was a part, is no longer part of Route 403. The two one-way lanes and two shoulders to the north toward Frenchtown Road and the on-ramp to Route 4 North before relocation now serve as two-way traffic with a lane and a shoulder in each direction. With relocation, traffic volume of 10,200 vpd was estimated to drop to 7,300 vpd.
Accelerated construction techniques reduced the time highway users were affected by more than 50 percent. The estimated roadway closure time for bridge construction would have been 6 months under non-accelerated construction. The actual impact on traffic lasted only 33 days, from July 30 to August 31, 2012.
The impact started when Davisville Road was closed to traffic on July 30, 2012, and the traffic was detoured. Figure 32 shows detours that were set in place. The primary detour route used Route 402 (Frenchtown Road) in East Greenwich and Route 1 (Post Road) and School Street in North Kingston. Motorists on Devil’s Foot Road (which turns into Davisville Road) could access the new Route 403 at West Davisville Road using the alternate route and take the exit for Route 4 North. They could also take the exit for Route 4 South to Route 402 (Frenchtown Road).
During the 33-day closure, detours eliminated traffic queuing and congestion at the construction site, allowing efficient installation of the modular bridge components.
The innovative accelerated bridge construction technique enabled reduction of the traffic detour duration by more than 80 percent, from an estimated 6 months for conventional construction to only 33 days.
Figure 32. Traffic management plan.
Researchers collected trip time data before Davisville Road was closed to traffic and during the closure. No queuing was observed on the primary or alternate routes. In general, the traffic flow along the both detour routes was light and flowed freely without backups or congestion at or above the posted speed limits.
The following nodes were established for trip time data collection:
When Davisville Road was open, the average travel time from Node 1 to Node 4 was 2.59 minutes based on morning, midday, and afternoon runs. Travel along the primary detour from Node 1 to Node 4 increased this average time from 2.59 to 5.26 minutes, an increase of 2.67 minutes. Travel along the alternative route averaged 3.99 minutes, an increase of 1.40 minutes.
The cost associated with the additional time to traverse the detour route is presented later in this report.
The load restrictions on the bridge because of structural inadequacy will no longer be needed. The new bridge meets all current standards for structural adequacy and is open to all traffic. Furthermore, motorists will notice a smoother ride when traversing the bridge because of its new asphalt surface.
The quality of the products used was superior because the contract required that the manufacturing plant furnishing precast bridge members be PCI certified at a minimum of B3 category. Furthermore, it required that dimensional tolerances not exceed those recommended in the latest edition of the PCI manual for quality control for plants and production of precast and prestressed concrete products. This assessment is based on the products meeting all specifications and the belief that disciplined procedures enforced at certified plants audited by external personnel are likely to yield better quality control than those at a construction site where quality control of concrete cast in place is dispersed among several entities and individuals. These personnel range from those at batch plants proportioning aggregates, cement, and water to drivers transporting the mixes in concrete trucks to inspectors responsible for ensuring that placing, compacting, and curing of concrete conform to specifications.
The September 7, 2012, AASHTO Journal Weekly Transportation Report, published by the American Association of State Highway and Transportation Officials, featured the Frenchtown Brook Bridge. The article includes the following quote from RIDOT Director Michael Lewis:
"Going into this project, we knew it would take only a third of the time to replace this bridge compared with the time it would have taken if we used traditional construction methods. We are pleased to be able to take this approach with the Frenchtown Brook Bridge and reopen it as quickly as possible for drivers in East Greenwich and North Kingston who rely on this bridge on a daily basis."
The article goes on to state, "The project was so successful that RIDOT noted it will evaluate all future bridge projects to see if they could be built using the ABC method."
It is clear from these statements that RIDOT is pleased with the decisions made on this project. It is also evident to the project team that absent formal user satisfaction surveys, based on the data and chart shown in Figure 33 and Figure 34, users of Davisville Road would be quite satisfied with RIDOT’s approach to minimizing the impact of construction on this project from 6 months for conventional construction to just 1 month using innovative ABC methods. Figure 33 and Figure 34 show results of a user satisfaction survey on a similar ABC project using precast components in Iowa. Clearly, the responses were positive (very important and important) on a number of decisions made on this project:
Figure 33. Rating of approaches to design, scheduling, and traffic management on projects.
Figure 34. Chart showing results of user responses on approaches to design, scheduling, and traffic management.