Tennessee

Overview of TIM Program

The Tennessee Department of Transportation (TDOT) operates four regional traffic management centers (TMCs), including ones in Nashville, Knoxville, Chattanooga, and Memphis. The TMCs cover a total of 342 centerline miles. The TMCs in Knoxville and Nashville operate 24 hours a day, 7 days a week. The TMCs in Chattanooga and Memphis do not operate during the overnight hours; overnight activity for these locations is monitored by the Knoxville and Nashville TMCs, respectively. TDOT operates a freeway service patrol, HELP, that patrols the most heavily traveled freeways in the regions where the TMCs are located. In an effort to maintain quick response times, HELP is typically constrained to operating on specific routes in the core areas of each city. HELP operates seven days a week, from the morning peak period (between 5:00 a.m. and 8:00 a.m. depending on location/route) through the evening peak period and beyond (between 8:00 p.m. and 10:30 p.m. depending on location/route). Also, HELP is often requested to work after hours for special events.[1]

Data Collection and Management

The TIM performance measures program in Tennessee was established through a formal stewardship and oversight agreement between TDOT and the Tennessee Division Office of the Federal Highway Administration (FHWA). While TDOT measured and tracked TIM performance prior to this agreement, the agreement formalized the process and made it mandatory. A memorandum of understanding (MOU) between TDOT and the Tennessee Department of Safety and Homeland Security, which includes the Tennessee Highway Patrol (THP), was put in place to provide guidance on clearing incidents on Tennessee highways. This MOU is titled “Urgent Clearance of Highway Incidents and Safety at Incident Scenes,” and it outlines the goal to clear incidents within 90 minutes. [2]

All four TMCs operate on the same incident data management system, which houses incident data and includes data elements associated with all three of the national TIM performance measures – roadway clearance time (RCT), incident clearance time (ICT), and secondary crashes. Generally, incidents are detected by the TMC operators, the HELP trucks, or the THP. HELP is able to communicate data in real-time from the field to the TMC operators. Once the TMC is aware of an incident, either through one of these three primary methods or another source, it is logged and tracked in the incident management system.

TDOT’s statewide TMCs are in their fourth year utilizing a web-based traffic incident locator, Locate/IM, which also has activity and reporting capabilities. Locate/IM provides real-time location information and reporting of traffic incidents and HELP Truck activity.[3] Locate/IM was integrated with the statewide TMCs for traffic incident management control and roadway monitoring, and it has removed all hand written documentation by HELP staff. Now, everything is entered into the database by a TMC operator while communicating with the HELP operators.

For crash reporting, the THP uses the Tennessee Integrated Traffic Analysis Network (TITAN), a centralized data and document repository developed for the electronic collection, submission, and management of all traffic safety related data in Tennessee. There is no integration between TITAN and TDOT’s incident management database; however, the TITAN crash reports are submitted electronically to the safety division of TDOT. THP may also enter incident records into the SWIFT system, which feeds into the Tennessee 511 system, but it is not yet integrated with the incident management system. TDOT is developing a new centralized ATMS that will integrate the statewide incident database with the 511 system. As the THP enters all incidents over 30 minutes into 511, the integration of the ATMS with the 511 system will allow TDOT to capture data on additional incidents. These data integrations will improve the quantity and quality of incident-related data for performance measurement.

As of 2015, all law enforcement agencies in Tennessee, by statute, must complete a new reporting section on the TITAN electronic form regarding roadway/lanes blocked due to traffic incidents and secondary crashes. These sections are used to collect data for the three national performance measures. The roadway/lanes blocked feature is shown in Figure 1. Officers enter the date and time of the first recordable awareness when traffic lane(s) were unavailable for traffic flow, the number of lanes blocked (numbered from left to right), the date and time of the first confirmation that all lanes are available for traffic flow (i.e., RCT), and the date and time at which the last responder has left the scene (i.e., ICT). An added benefit to this approach is that it provides Tennessee with the data to examine TIM performance by the number of lanes blocked.

Figure 1. Roadway/Lane Blockage Entry Feature in TITAN

Figure 1. Roadway/Lane Blockage Entry Feature in TITAN

Regarding secondary crashes, TDOT and THP originally had different approaches/definitions of a secondary crash. After TDOT shared its secondary crash definition (which is consistent with FHWA’s definition) with the THP, the THP modified its definition to match that of TDOT. All employees were trained on the definition during the TIM training, and the TITAN client now has the required feature of collecting secondary crash information. Within the TITAN client, a secondary crash is defined as: “a crash occurring within an incident scene or within a traffic backup (queue), including the opposite direction, resulting from an original incident. Officers are instructed that the original incident does not have to be a collision; it could be a disabled vehicle, vehicles on the side of the road, construction/maintenance zone, a traffic stop by law enforcement, or any other unusual circumstance related to traffic backup or change in traffic flow as long as it played a role in distracting the driver or the causation in the collision.

When completing a report in TITAN, officers are asked to indicate (yes or no) to the question “is this a secondary crash?” If the officer selects, “yes,” he/she is required to enter a “secondary type from the following options: crash nearby, construction zone, maintenance zone, law enforcement action, or other (Figure 1).Tennessee’s approach to identifying and recording secondary crashes is that, while it is not an exact science, it is important to identify secondary crashes as best as possible in order to bring them to light.[4]

Figure 1. Secondary Crash Entry Feature in TITAN

Figure 1. Secondary Crash Entry Feature in TITAN

TDOT maintains an internal performance goal to open travel lanes within 90 min for 94% of all incidents. TDOT tracks performance towards this goal via the RCT performance measure and strives to make improvements if the goal is not being met. In the past, TDOT has implemented training and expanded HELP coverage in urban areas to help reduce RCTs and improve performance.

Performance Analysis and Reporting

Through the Locate/IM database, each regional system has the capability to produce a quarterly report indicating total incidents managed, number of incidents by type and detection source, number of travel lane blockage incidents, percentage of incidents by RCT, number of incidents by type of HELP service provided, events affecting traffic, and DMS usage. The system allows for a statewide quarterly report to be generated combining each region’s information.[5] The graph shown in Figure 3 was extracted from the TDOT Region 1 Quarterly Report for Quarter 4, 2014.[6] This graph shows the percentage of incidents in each of four lane blockage clearance categories: 30 minutes or less, 31-60 minutes, 61-90 minutes, and over 90 minutes.

Figure 3. TDOT Region 1 Quarter 4, 2014, Lane Blockage Clearance Times

Figure 3. TDOT Region 1 Quarter 4, 2014, Lane Blockage Clearance Times

Benefits of TIM Performance Measurement

The collection and reporting of data on TIM performance in Tennessee has led to increased participation in TIM discussions within the urban areas, including representation from groups not previously engaged. This increased participation has expanded and enhanced TDOT’s relationships with partner agencies. TDOT also has been able to use the data to demonstrate the value of the TIM program to decision makers. More specifically, the data helped justify funding and expansion of the HELP program. HELP staff is now allowed to take trucks home to support on-call 24/7 operations. Additionally, two of the TMCs now operate 24 hours, 7 days a week.

Data on secondary crashes has also helped support analysis of the effectiveness of TDOT’s Protect the Queue Program, launched in June 2013. A serious secondary crash on I-24, a “turning point” for TDOT, spurred the creation of the Protect the Queue Program. This fatal secondary crash resulted from a tractor-trailer running into the back of a queue of slow moving traffic due to a non-injury incident up ahead. The Project the Queue Program stresses to all TDOT employees and partnering agencies the importance of protecting drivers caught in a traffic queue and involves a training program on the most effective queue management techniques. Since the start of TDOT’s Protect the Queue campaign, data gathered between July 2013 and December 2013 showed a 19 percent reduction in secondary incidents as compared to the same period in 2012, equating to 20 fewer secondary incidents and potentially four lives saved. The secondary crash data for this analysis were retrieved from THP’s TITAN system.[7]

 

[1] Tennessee DOT, How does the HELP Program work?, https://www.tn.gov/tdot/topic/help-program-work, accessed February 2016.
[2] Tennessee DOT and Tennessee DOSHS, Urgent Clearance of Highway Incidents and Safety at Incident Scenes, https://www.tn.gov/assets/entities/tdot/attachments/MOU-TDOT-TDOSHS-Feb-14-2012.pdf.
[3] Tennessee DOT, Tennessee Department of Transportation HELP Program and Transportation Management Centers Annual Operations Report – July 1, 2013-June 30,2014, December 2014, https://tn.gov/assets/entities/tdot/attachments/2014HELPTMC-OperatingReport.pdf
[4] Tennessee Highway Patrol, Collection of Secondary Crash Information and Roadway/Lane Blockage within TITAN Client, document provided to FHWA in July 24, 2015, email.
[5] Tennessee DOT, Tennessee Department of Transportation HELP Program and Transportation Management Centers Annual Operations Report – July 1, 2013-June 30,2014, December 2014, https://tn.gov/assets/entities/tdot/attachments/2014HELPTMC-OperatingReport.pdf
[6] Tennessee DOT, TDOT Region 1 Quarterly Report, Quarter 4, 2014, http://www.tn.gov/assets/entities/tdot/attachments/Reg1Q4TMCReport.pdf.
[7] Tennessee DOT, Tennessee Department of Transportation HELP Program and Transportation Management Centers Annual Operations Report – July 1, 2013-June 30,2014, December 2014, https://tn.gov/assets/entities/tdot/attachments/2014HELPTMC-OperatingReport.pdf