Automated Work Zone Information System on Urban Freeway Rehabilitation: California Implementation

In October 2004, about 9 lane-km of deteriorated truck lanes on Interstate-15 (I-15) at Devore in Southern California were rebuilt during 18 days using extended one roadbed full-closures with the counter-flow traffic system and 24/7 construction operations. The project implemented the Automated Work Zone Information System (AWIS) to reduce peak hour delay during construction by changing road user’s travel patterns and diverting traffic to detour routes. This paper describes the design, performance, and validation of AWIS using monitored traffic data before and during construction. The AWIS was installed to provide road users with real-time travel information so that they could avoid traffic delays in the Construction Work Zone (CWZ) corridor. Travel times through the CWZ were estimated from speed data and enhanced in two ways: (a) portable and permanent changeable message signs on site, and (b) off-site (the project website) implementation with travel time messages, traffic snapshots, and video streaming. AWIS travel time estimated to be 90 percent of the actual travel times as measured by probe vehicles. The peak hour traffic demand through the CWZ was reduced by 17.5 percent with significant volume increases to detour freeways. The AWIS operation contributed to a decrease in the maximum delay for weekday peak hours (from 90 minutes to 45 minutes on average during construction). The outcome of this case study will help transportation agencies and practitioners efficiently design and operate AWIS for highway rehabilitation under high traffic volume. TRB 2006 Annual Meeting CD-ROM Paper revised from original submittal. 06-2636: Lee and Kim 3 ITS ON HIGHWAY CONSTRUCTION PROJECTS Many U.S. highway pavements, built during the infrastructure construction boom between 1955 and 1970, have now exceeded their original 20-year design lives and have been subject to far greater traffic demands than were initially envisioned. The deterioration of these highway pavements hurts driving safety and ride quality. In recent years, state highway agencies have shifted their focus from building new transportation facilities to “4-R” type projects emphasizing restoration, resurfacing, rehabilitation, and reconstruction of existing roadways (1). Because construction activities decrease road capacity and interrupt traffic flow, construction work zone (CWZ) closures impeded traffic flow. Therefore, traffic management plans (TMP) for CWZ should be developed with a priority on minimizing road user costs (RUC). However, for most rehabilitation projects engineers depend upon their judgment from previous experience, rather than following a well-defined and reliable process using analytical tools to develop TMP and select rehabilitation strategies (2). Traffic analysis methods and tools are needed to quantify the RUC associated with various types of highway rehabilitation and to help the agency develop TMP to effectively minimize costs. Researchers and practitioners are developing TMP to mitigate traffic delays caused by such closures, especially in urban highway networks. To help mitigate traffic delay problems, intelligent transportation systems (ITS) are being utilized in a variety of transportation fields. As one of the more effective ITS technologies, an Automated Work zone Information System (AWIS) has been developed and employed in urban freeway construction activities. AWIS consists of traffic data collecting devices to monitor traffic conditions, changeable message signs to display traffic information, and a server computer to calculate estimated travel times in the designed algorithm. The main purpose of AWIS is to communicate real-time travel information to road users heading into the workzone corridor so that they may decide whether to take a detour route or continue through the CWZ. Several state agencies, including Arkansas, Nebraska, and California, have conducted research into AWIS performance. Fontaine reviewed applications and results of Work Zone Intelligent Transportation Systems (WZITSs) in several states and provided an application guideline of WZITS (3). However, the author concluded that testing result did not show conclusive benefits at all sites. He determined that more objective research was required to fully assess the potential of these systems. In 2000, an AWIS was implemented for a highway reconstruction project along a rural work zone of Interstate-40 (I-40) in Arkansas. The major purpose of this AWIS was to increase work zone safety by reducing crash potential at the end of queues (4). The system generated a message warning road users to reduce speed as they approached the CWZ. The AWIS was installed upstream of the CWZ and compared traffic backups indicated by the AWIS with backups observed in the field. Changeable Message Signs (CMS) were deployed to provide speed advisories along the CWZ corridor. The researchers found that backups formed at short term flow rates between 800 and 900 pce/h (passenger car equivalents per hour). California Department of Transportation (Caltrans) evaluated an AWIS device called the Computerized Highway Information Processing System (CHIPS), which was deployed on the Interstate-5 (I-5) construction project in Southern California. The criteria used in judging its effectiveness included the system’s impact on traffic diversion, its capacity to improve the safety for road users and construction personnel, and the responses it elicited from travelers (5). Traffic diversion was observed on two evaluation dates and Caltrans concluded that the use of AWIS TRB 2006 Annual Meeting CD-ROM Paper revised from original submittal. 06-2636: Lee and Kim 4 succeeded in providing a safer CWZ environment. Traffic volumes measured on exit ramps located upstream of the CWZ were compared with traffic volumes in non-construction conditions. The higher traffic volumes observed on the exit ramps duringAWIS operation indicated that the system had effectively diverted traffic away from the CWZ. These recent studies were primarily focused on increasing safety in the CWZ by warning of traffic delays, rather than on implementing information systems designed to divert traffic to detour routes in the network. They deployed CMS along the upstream of CWZ corridors but not along other freeways within the network as would have been required for the purpose of checking traffic flow and encouraging diversion to other routes. These CMS did not display dynamic (real-time) travel information but instead displayed static delay messages. In these earlier implementations, travelers couldn’t change their travel patterns, travel modes, or departure times in advance since no off-site (on-line) traffic information was provided during construction. This earlier research into the potential of AWIS was thus limited by its scope and did not provide concrete data with which to measure the benefits of AWIS operation. The AWIS introduced in this case study on the I-15 Devore reconstruction project was designed as a far broader implementation, providing travel time estimates to road users in real time, both on site through the use of CMS, and off site (online) through the implementation of a project web site. I-15 DEVORE RECONSTRUCTION PROJECT The I-15 Devore pavement reconstruction project is located on I-15 between Interstate-10 (I-10) and Interstate-215 (I-215) in San Bernardino County, California (see FIGURE 1). The I-15 Devore corridor, with three or four lanes in each direction, carries a traffic volume of approximately 110,000 Average Daily Traffic (ADT), about 10 percent of which are heavy trucks. In contrast to typical urban freeways in California, this corridor has high leisure traffic volume on weekends. Since leisure travelers in the Los Angeles area are going to and from Las Vegas through this corridor, the highest traffic volumes northbound (NB) appear on Friday and the highest traffic volumes southbound (SB) appear on Sunday. In October 2004, Caltrans rebuilt a 4.5-km section of the deteriorated concrete truck lanes within two 210-hour (about 9 days) extended closures using around-the-clock (24/7) operations. According to the pre-construction analysis, the project would have taken about 10 months using the traditional approach of nighttime closures (6). For the full closure (called “extended closure” hereafter) of one roadbed for construction, the traffic was diverted to the other side on the traffic roadbed through median crossovers, using the counter-flow traffic system. The traffic roadbed had five lanes, including one temporary lane converted from the shoulder rehabilitated with asphalt concrete. The five lanes of the traffic roadbed were then converted to two-way traffic (two by three lane configuration) using Quickchange Moveable Barriers (QMB) as a “counter flow traffic” control system (FIGURE 2). The QMB provided three lanes to the commuting traffic direction during every peak period (three lanes SB in the morning and three lanes NB in the afternoon). The QMB was shifted twice a day in an operation that took less than 30 minutes in live traffic. This dynamic lane configuration (three by two lanes) was routinely accomplished without interruption of traffic. TRB 2006 Annual Meeting CD-ROM Paper revised from original submittal. 06-2636: Lee and Kim 5 FIGURE 1 Location of the Traffic Devices Employed in the Study Area. FIGURE 2 Dynamic Lane Configuration with the Operation of Quckchange Moveable Barrier. TRB 2006 Annual Meeting CD-ROM Paper revised from original submittal. 06-2636: Lee and Kim 6 Pre-construction traffic analysis, using a demand-capacity (D-C) model based on the Highway Capacity Manual (HCM 2000) with hourly traffic data collected in March 2002, was performed for the extended continuous closure scenario to estimate the maximum delay during peak hours. The estimated maximum delay within the CWZ was 95 minutes for NB traffic during the weekday afternoon peak when a 10 percent reduction of traffic wa