US-23 Flex Route First Active Traffic Management (ATM) System in Michigan

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1 Jennifer Foley Michigan Department of Transportation, Jackson, Michigan United States of America Karianne Steffen, P.E. PTOE HNTB Michigan, Inc West Road Building 2, Suite 202 East Lansing, MI United States of America Stephanie Palmer, P.E. Michigan Department of Transportation, Jackson, Michigan United States of America Abstract In an effort to mitigate congestion issues and improve travel time reliability along the US-23 corridor, the Michigan Department of Transportation (MDOT) has installed the first deployment of active traffic management (ATM) branded as the Flex Route. The project extends from the western US-23/M-14 tri-level interchange to just south of M-36 (9 Mile Road) (approximately 8.5 miles), north of Ann Arbor. The project upgraded the median shoulders and installed lane control gantries along the corridor to allow the median shoulder to be used as third lane of travel during peak traffic conditions. The US-23 Flex Route utilizes overhead gantries equipped with various intelligent transportation systems (ITS) equipment to facilitate the following ATM strategies, dynamic shoulder use, dynamic lane control, variable speed advisories, queue warning, real-time truck parking information and management systems (TPIMS) and overheight vehicle detection system. The project team overcame several challenges during the planning, design, construction, and system management phases of the project, which included the following: The development of design specifications pertaining to using a median shoulder as a travel lane Gantry spacing and placement Lane Control Sign and Dynamic Message Sign Standard Messaging Regulatory Signing and Pavement Markings Advanced Traffic Management System Software Upgrade/Integration Cost Effective Power and Communication Considerations Using Existing Devices in New Ways Safe Dynamic Shoulder Lane Endings Standard Operating Procedures Opening the Shoulder (clearance procedures) Testing During Construction Winter Operations Lessons Learned KEYWORDS: Active Traffic Management Transportation System Operations Emerging Technology Transportation System Operations Background Active Traffic Management is the ability to dynamically manage recurrent and non-recurrent congestion using technology and operational strategies. US-23 Flex Route uses several ATM strategies: dynamic lane control, dynamic shoulder use (also known as part-time shoulder use or hard shoulder running), variable speed advisories, and queue warning. Dynamic shoulder use allows driving on the shoulder during certain times of the day. The US-23 Flex Route utilizes gantries over the roadway with lane control signs over each lane to indicate if the lane or shoulder is open to traffic. MDOT selected dynamic shoulder use due to peak directional traffic, crash history, and stop and go congestion. The deployed ATM strategies are providing additional capacity, improved incident response, speed harmonization, and advance notice to drivers of upcoming conditions. The US-23 Flex Route is between Brighton and Ann Arbor in MDOT s University Region. The corridor is approximately 9 miles in length, from M-14 to M-36. US-23 has heavy peak directional traffic southbound in the morning and northbound in the afternoon. Previous studies along US-23 have indicated that widening this corridor to three lanes in each direction would result in significant environmental and right-of-way impacts. An environmental assessment was conducted selecting ATM as the preferred alternative. 1

2 Design In conjunction with MDOT, industry experts, and peer states, many design criteria and standards for ATM corridors such as pavement markings, static signing, guidelines for spacing of gantries near bridges and ramps, and dynamic lane control sign messages were established throughout this project. MDOT is already moving forward with concept exploration on their second Flex Route project, which is utilizing many of the concepts and standards developed on US-23 Flex Route. Design coordination meetings included representatives from additional regions and business areas not part of the US-23 Flex Route to ensure the established design criteria would work for more projects than the immediate needs of US-23. Michigan was one of the first states to use active traffic management in the left or median shoulder. Historically other states have utilized hard should running on the right shoulder. Due to the geometrics of the US-23 corridor, use of the right shoulder would have been more costly. MDOT determined that the left shoulder would be the best for the active traffic management applications. MDOT studied left shoulder use that was utilized in Minnesota implemented lessons learned to develop the Flex Route on US-23. During discussions with Minnesota MDOT had to determine what the best pavement markings would be for the left shoulder. It was determined that a four inch solid yellow pavement marking was best to separate the shoulder lane from the general purpose lane. Since the shoulder was only to be used part time that the pavement marking should remain yellow to indicate that the shoulder lane was a shoulder when not in use. When the shoulder lane ends and opens to a general purpose lane the pavement marking goes from a solid yellow to the standard white skips. A regulatory sign was also needed so that drivers knew when it was allowed to drive on the shoulder. Shoulder Use Permitted on Green Arrow Only signs were designed and installed on each entrance ramp, as well as when driver s enter the corridor on US-23. Figure 1: Solid yellow pavement marking, 60 mph advisory speed Since MDOT had determined to utilize the left shoulder, the Federal Highway Administration (FHWA) required MDOT to perform design exceptions for lane and shoulder width. The left shoulder was constructed with an eleven (11) foot lane with a two (2) foot shy distance to the barrier. As part of the design exception, MDOT agreed to install six (6) crash investigation sites throughout the corridor to aid in clearing for incident management. Due to the lack of additional shoulder width MDOT agreed to place a maximum advisory speed of 60 mph throughout the corridor. Another challenge MDOT faced was getting this information back into the State network. The fiber optic cable plant is configured in a way to provides redundancy along the corridor with Layer 3 Ethernet switches at each device location. For backhaul, two dedicated leased Ethernet Private Line Services (EPLS) at opposite ends of the corridor provide redundant links to the State of Michigan ITS Network, accessed from their Statewide Transportation Operations Center (STOC). Coordination was required with the Department of Technology, Management and Budget (DTMB) for security, speed, and reliability of the EPLS. Gantry Details A standard MDOT truss was selected as the gantry to attach the lane control signs over each lane of traffic. This required power and communications cabling to go up the vertical member of the truss and across the truss box to each lane control sign. Aesthetics of the gantry were considered while designing the mounting details for power and communications. Special details were also required to mount the low light camera to the truss for viewing the median shoulder and MVDS bracket arm to detect traffic speeds and occupancy of all lanes for each direction. 2

3 After several discussions with other states it was also determined that the gantries should be spaced every half mile. In order to effectively manage traffic during an incident the gantries needed to be spaced so that the driver could see the next lane control sign indicating lane assignment. Due to several bridges, curves and elevation changes within the corridor the layout of the gantries was an iterative process to optimize viewing, access to power, and maintain half mile spacing. Low Light Cameras Figure 2: Junction box and conduit Since the corridor does not have continuous freeway lighting, a solution was needed to see in the dark to be able confirm the shoulder is clear of obstructions prior to opening. Due to the dark winter condition in Michigan, peak periods can occur early in the morning or late in the evening when day light hours are limited. The MDOT ITS Program Office utilized their test bed to assess several low light camera options. Once the technology was confirmed to work, a special provision was written to be included in the project. MDOT has developed camera tours for segments of the corridor to run prior to opening the shoulder. In addition to the low light cameras located on every gantry, MDOT also has cameras placed on ninety foot spun concrete poles to aid in visual overviews of the corridor. Figure 3: Low light camera fixed to gantry Figure 4: Image from low light camera 3

4 Maintenance Efficiencies The system was designed with lane control sign guts in the cabinets protected with guardrail to minimize disruption to traffic when maintenance is needed. Most work can be completed to fix the lane control signs without closing a lane of traffic. This is for the safety of workers as well as to keep the traffic flowing without disruption. Remotely controlled power distribution units and hardened computers were included in ITS cabinets to decrease maintenance response time. MDOT s ITS maintenance contractor can remotely access all ITS equipment on US-23 and troubleshoot any problems quickly, with the ability to power cycle devices without driving to the site and impeding traffic. MDOT is currently tracking how much time and materials is utilized to maintain the system in order to develop an innovative contracting solution for the maintenance of this system. Software Software to operate the ATM system was developed as part of the project. Software development included coordination with other MDOT regions that may utilize ATM strategies to make the software as flexible, scalable, and user friendly for US-23 as well as future ATM projects. The new module added into their existing Advanced Traffic Management System (ATMS) software package includes response plans to open the shoulder during peak periods and as-needed, an algorithm to analyze real-time data and propose advisory speeds to harmonize traffic flow, and logic for dynamic response plans to react to incidents that may require lane closures and/or shoulder opening. User acceptance testing and training was also needed to confirm software functionality and to prepare the operators at MDOT s Statewide Transportation Operations Center (STOC). Figure 5: Testing of software Standard Operating Procedures and Quick Reference Guides Standard operating procedures (SOP) were developed to define procedures for Flex Route operators. The SOP include definitions, maps, graphics of what the system should look like, and procedures for each scenario an operator might encounter. Knowing that Flex Routes will be part of MDOT s tools to address increasing congestion and problem areas, the procedures cover operation of ATM strategies at a general level, with specifics to each corridor noted in the procedures. This way, the SOPs are flexible and scalable to additional deployments without having to rewrite the book. The quick reference guides (QRG) were also developed which concise step by step guides that are meant to be a quick aid that an operator can flip through as a reminder of the steps and expected outcomes of each procedure without having to reference the full SOP. They include tips and graphics from the ATM software to help guide operators through common processes, creating consistent operation and reliable messages. US-23 Flex Route will expose many drivers to active traffic management. Each time a driver uses the system, they will become more familiar and trusting of the information provided. Construction This project required extensive coordination of the road, drainage, bridge, and lighting plans prepared by MDOT; ITS, freeway signing, and bridge plans prepared by HNTB; and, signal plans, ramp extensions, and public involvement activities by other consultants. Because all of this was combined into one construction bid package, it was essential that the plans, special provisions, and cost estimates be coordinated at a high level to avoid the possibility of contractor claims during construction due to inconsistencies in the contract documents. This coordination was achieved through 4

5 a series of regularly scheduled coordination meetings, project consistency reviews, and use of MDOT ProjectWise for file sharing. Due to an expedited schedule for construction, the design assistance during construction and system management part of the project was accelerated including shop drawing reviews and acceptance testing. ITS projects require the contractor to submit shop drawings of equipment for approval by MDOT s system manager. This project required all submittals in 30 days following award, which is significantly faster than standard ITS projects. In addition to the shop drawing submittals, the Contractor was required to meet several interim deadlines within the contract in order to receive incentives, or they faced liquidated damages. Testing was also compressed with multiple testing on the same day: local testing, sign commissioning, and fiber optic testing requiring numerous qualified staff. Testing all equipment was required to confirm functionality in the field as intended. Local device testing ensures each device meets requirements, subsystem testing confirms each device can be communicated with, and final system testing verifies the system all works together. Testing was complicated with vehicles traveling the corridor during construction with potentially confusing or conflicting messages needing to be posted on lane control signs. A system of dots was used to simulate final messages and testing in progress posted on dynamic message signs to continue testing during construction. This way when the roadway work was complete, the ATM system was ready to use. Figure 6: Graphic s used during testing of software In addition, utility coordination was a key for the project success. Several on site meetings had to occur with each utility company to obtain power for all new sites as well as for relocation of existing utilities. Utility coordination began very early in the development stages, and utility companies were required to relocate existing utilities prior to the construction project letting. Traffic Operations Dynamic Message Signs (DMS), Microwave Vehicle Detection Systems (MVDS), Closed Circuit Television (CCTV) cameras, and fiber optic cable are all being used on the project and aren t new for MDOT; however, each device is being used in a new and innovative way. The DMS used are full color LED lane control signs above each lane to provide graphical information for drivers. Dynamic lane control combined with dynamic shoulder use will improve traffic conditions during incidents by safely moving traffic around a crash. The use of variable speed advisories and queue warning will reduce secondary crashes by providing advance notice of conditions such as which lane is affected and warnings to reduce speed. 5

6 Figure 7: Gantry with ITS equipment being used (LCS, DMS, MVDS, and CCTV) Real-time data is being used to actively manage traffic to open the shoulder, harmonize speeds, warn drivers of conditions ahead, and respond to incidents. With the use of Microwave Vehicle Detection Systems (MVDS), speed and vehicle density is provided for the software to analyze for variable speed advisories and if traffic conditions meet thresholds to open or close the shoulder lane. MDOT analyzed the volume data and determined the thresholds for both northbound and southbound US-23. In an effort to utilize the hard shoulder and improve the capacity of the corridor MDOT determined that the operating times from the thresholds displayed below. During development of the software it was also determined that the maximum speed displayed on the corridor would be 60 mph (posted speed is 70 mph). This was an agreement made between MDOT and the Federal Highway Administration (FHWA due to the design speed of the shoulder. A queue warning system was implemented in an effort to reduce rear end crashes. The queue warning system is automatically detected when speeds drop below 60 mph. The software will prompt the operator to active the variable speed limit (VSL). As speeds drop the software reduces the speeds on the signs in increments of 10 mph. Figure 8: US-23 Flex Route Speed Thresholds In addition to utilizing the VSL for speed harmonization, MDOT has worked closely with the Michigan State Police (MSP) to determine safe thresholds during winter storm events. Michigan roads can be hazardous and in order to aid the driver with information during winter storm events the maximum speed will be posted at 40 mph per the direction of MSP. The VSL will return to automatic operating procedures as the conditions improve. System Benefits Within the United States there have been limited facilities where Active Traffic Management has been implemented. In the locations where ATM has been implemented, the strategies have varied between locations. A publication by the Federal Highway Administration titled Integrating Active Traffic and Travel Demand Management: A Holistic Approach to Congestion Management (1) found the following system benefits for facilities that have implemented ATM: 6

7 Increase in average vehicle throughput of 3 to 7 percent Increase in overall capacity of 3 to 22 percent Decrease in primary incidents of 3 to 30 percent Decrease in secondary incidents of 40 to 50 percent Overall harmonization of speeds Increase in trip reliability Furthermore, the Highway Capacity Manual (HCM 2010) (2) supports the use of ATM strategies for incident management by indicating that ATM strategies may be included as part of an overall incident management plan to improve facility operations during and after incidents. According to the HCM 2010 (2), ATM can increase capacity of a facility due to a dynamic traffic lane, speed harmonization, and an increased incident response time. The capacity of a dynamic shoulder was not detailed with the HCM, however, information from other states have indicated that the maximum capacity of a dynamic shoulder is approximately 1,700 (as compared to 2,000 for a freeway lane). With this added capacity to the system during peak period, this adds a huge benefit to operations along a corridor. Incident Management Although the results for the corridor indicates that the implementation of ATM would produce an impact over the normal operations during the peak periods, the greatest operational benefit is expected to occur when managing incidents along this corridor. Capacity reductions, such as a stalled vehicle on the outside shoulder, create unstable traffic flow resulting in stop and go traffic. When an incident occurs that closes a travel lane, significant backups and delays occur. With the use of the shoulder as a method to assist in clearing traffic during even minor traffic incidents it is anticipated that this nonrecurring congestion related to incidents will be significantly reduced. As the recurring and nonrecurring congestion along US-23 improves, this should also result in an increase in air quality and a reduction of noise along this corridor. Dynamic lane control combined with dynamic shoulder use will improve traffic conditions during incidents by safely moving traffic around a crash. The use of variable speed advisories and queue warning will reduce secondary crashes by providing advance notice of conditions such as which lane is affected and warnings to reduce speed. Safety Benefits In addition to operational benefits anticipated from implementing ATM along this corridor, there are potential safety benefits. Many previous ATM implementations have documented crash reduction factors after implementation. There has been very little documented on the reduction in crash rates due to the installation of ATM within the United States. Information from other states (particularly Minnesota) has shown that introducing ATM along a corridor with dynamic shoulder lanes, lane control, and variable speed limits could reduce crashes up to 20 percent. A crash analysis was performed on the proposed corridor along northbound and southbound US-23 from the M-14/US- 23 wester junction to the M-36/9 Mile Road interchange. Crashes were pulled from January 1 st 2008 to December 31 st 2010, which was the most recent three (3) year period where this corridor was not impacted by construction. Since the Active Traffic Management lanes would only be open during peak hours and for incident management, only the peak hours from 6:00 am to 9:00 am and from 3:00 pm to 7:00 pm were analysed. The following types of crashes were investigated: Rear-end Straight Side-Swipe Same Fixed Objects There were a total of 373 crashes throughout this corridor, of the total there were 88 injured. There were 64 fixed object type crashes, 224 rear-end straight type crashes, and 41 side-swipe same type crashes; which resulted in 74 injuries. It is anticipated that when ATM is in place, a 20% reduction in crashes for fixed object, rear-end straight, and sideswipe same will apply. Performance Monitoring In order for the Flex Route to be successful, it must be actively managed. Since the commencement of the Active Traffic Management along US-23 MDOT has developed procedures to monitor travel times, planning time index, 7

8 speeds along the corridor, crash history, and operation and maintenance costs. MDOT has also decided to solicit feedback from the public, local agencies and emergency responders. Travel time reliability and safety The main goals of the US-23 Flex Route project are travel time reliability and safety. Dynamic shoulder lanes are expected to reduce congestion during peak periods and special events, improve travel time reliability by providing consistent conditions, and reduce crashes by providing speed advisories and advance notice of conditions ahead. The dynamic shoulder use strategy will provide an additional lane of traffic during the peak periods, special events, and unexpected congestion. The variable speed advisory and queue warning strategies will convey speeds to reduce stop and go conditions and messages such as Stopped Traffic/2 miles ahead. And dynamic lane use will direct traffic around major incidents to improve traffic flow and safety of first responders. Nobody likes being stuck in traffic and everyone wants to be safe when on the road. With more consistent traffic conditions, improved incident management during major incidents, and safer road maintenance, the benefits to society are numerous. Reliable travel times, less congestion, and safer roads are anticipated to lead to an economic boost, through fuel savings, emissions reduction, people and freight on time, and improved safety. The Michigan Department of Transportation will continue to monitor the operations, maintenance costs and safety of the roadway. References 1. Integrating Active Traffic Management and Travel Demand Management: A Holistic Approach to Congestion Management, Federal Highway Administration, January Highway Capacity Manual 2010, Federal Highway Administration, December