Transit Management

EMTRAC Transit Signal Priority

EMTRAC Transit Signal Priority (TSP) in the Field

The EMTRAC system utilizes reliable GPS technology and secure frequency-hopping spread spectrum radio to enable both transit bus and rail vehicles to request priority through signalized intersections.

Transit Signal Priority with EMTRAC TSP

Signal Priority without Traffic Disruption

Vehicles with the EMTRAC system transmit a priority request to equipped intersections when passing through detection zones. The intersection-control cabinet contains an EMTRAC Priority Detector, which relays the priority-request to the signal controller.

EMTRAC is completely automatic and requires no driver interaction. In addition, EMTRAC can be configured to allow priority control based on time of day, route-schedule adherence, passenger load, direction traveled, or other factors.

Adaptive Priority

Adaptive priority is a strategy for adjusting signal control based on real-time traffic conditions. "Its application to TSP continuously optimizes the effective timing plan based on real-time, observed data, including transit vehicle location."[3]

EMTRAC Estimated Time of Arrival - Adaptive Priority

Arrival times vary according to traffic conditions and are reported by EMTRAC-equipped buses.

The EMTRAC system provides the data needed to implement, or improve, adaptive systems by notifying the signal controller when an approaching bus reaches pre-defined ETA timepoints during its approach (for example, when it is 90, 60, 35, and 15 seconds from the intersection).

This system is unique to North America and takes advantage of features built into many signal controllers and TSP firmware. It reacts to changes in on-street congestion and bus-approach speeds in real time. As traffic volumes fluctuate, so do the positions of ETA time-points.

Upon receiving the bus ETA notifications, the traffic controller preconditions its internal timings in preparation of its arrival at the intersection. The advanced time-points help the signal controller gradually modify the timings to reduce the impact on the intersection while also maintaining coordination with other intersections along the corridor.

Applicable Patent: US No. 8,878,695

Conditional Priority
EMTRAC Conditional Transit Bus Priority

EMTRAC-Equipped BRT, Brampton, ON (photo by Sean Marshall)

Conditional priority utilizes real-time vehicle status to determine whether signal priority should be requested—and it is often the best solution for achieving effective transit performance with minimal traffic disruption.

According to ITS America, "Conditional priority means that a smaller percentage of transit vehicles are requesting priority, but may be viewed as preferable if the emphasis is more on improving service reliability than on decreasing absolute travel time."[3]

In addition to many other possible conditions, TSP may be based on the following:

  • Time Behind Schedule
  • Time Since Last TSP Request
  • Door Status (open or closed)
  • Stop-Request Status
  • Passenger Load (Total or Percentage)

The EMTRAC system is capable of handling conditional factors in a number of methods—depending on your available capabilities. These methods include:

  • Connection to Onboard Transit Computer: The transit computer outputs conditional status to the EMTRAC Vehicle Computer Unit (VCU). For example, the transit computer determines that the bus is five-or-more minutes behind schedule and outputs this status to the EMTRAC VCU, which requests priority until the bus status is once again within the pre-defined time frame.
  • EMTRAC Priority Detector Determines Status: The intersection-based Priority Detector calculates the conditional status and responds accordingly. For example, if a bus on Route 180 has requested priority at a given intersection within the last five minutes, the Priority Detector does not forward priority requests from Route 180-buses during the pre-defined time frame.
  • AVL System Determines Status: EMTRAC Central Monitor (or third-party transit AVL system) determines vehicle and/or intersection states and outputs that data to the intersection-based Priority Detector, which carries out (or withholds) priority requests as a result.

For information about how the EMTRAC system is used to generate conditional priority in Brampton, Ontario, please read the Transit Applications and EMTRAC System white paper.

Actuated Priority

Actuated transit phases allow equipped buses to request priority for specific intersection lanes. For example, left-turn lanes are given signal priority when buses enter the pre-defined left-turn zone and request priority for that specific lane.

EMTRAC utilizes multiple global navigation systems, augmented by inertial navigation (three-axis gyro and accelerometer), to deliver precise actuated priority requests.

Actuated Left Turns and Queue Jump Lane for Transit Signal Priority

Actuated Left-Turns (A) and Queue-Jump Lane (B) Transit Priority

Actuated transit phasing may be implemented with the EMTRAC system in the following ways:

  • Exclusive Left Turn Lanes: Use EMTRAC software to easily define any left-turn lane to allow TSP without affecting other lanes and phases.
  • Queue Jump Lanes: Grant lead-phase priority to buses at near-side stops, bays, and lanes to allow them to re-enter mainstream lanes before general traffic.
  • Freeway Ramp Meters and Queue Bypasses: Enable equipped buses to reduce freeway ramp meter wait times. In areas with queue bypass lanes, request priority for the bypass lane without affecting the mainstream ramp lane.
  • Gate-Controlled Lanes or Garages: Request gates to open for equipped vehicles—without requesting access to nearby vehicles that are not adjacent to the gates.
  • Conditional Signal Priority enables equipped vehicles to request priority only when agency-specified conditions are met.
  • EMTRAC ETA technology enables traffic agencies to implement Adaptive Signal Control for intersections, including those not equipped with adaptive-capable controllers or other third-party inputs. The ETA feature updates controllers of calculated time-of-arrival based on current traffic conditions (U.S. Patent No. 8,878,695).
  • Systems Manager interface allows easy customization for individual vehicles, vehicle classes, or intersections. For example, rapid transit buses may request signal priority earlier than local metro buses.
  • Precise satellite and inertial positioning enable actuated requests by lane, even in the most difficult conditions (such as in urban canyons or under large overpasses).
  • Detailed logs and reports show vehicle and intersection activity by date and time. The EMTRAC system may also automatically email periodic reports to specified personnel.
  • Priority-request start points may be based on time-of-day to allow for earlier controller requests during peak-period rush hours.
  • The benefits of TSP are well documented—and EMTRAC-system features reduce traffic disruption and unsynchronized signals
  • Installation and maintenance time is significantly less than with any other TSP system.
  • Offers the most advanced TSP features without requiring the latest signal-controller equipment.
  • Improves schedule adherence and headway times by enabling transit vehicles to request priority only when behind schedule.
  • Helps reduce fuel costs by decreasing intersection delays.
  • Interfaces with EMTRAC Central Monitor to enable transit personnel to track vehicle progress and activity.

EMTRAC for Bus Rapid Transit (BRT)

The EMTRAC system is uniquely capable of helping buses take full advantage of existing BRT features while helping transit agencies implement a high-quality "transit system that delivers fast, comfortable, and cost-effective urban mobility."[1]

EMTRAC Bus Rapid Transit Signal Priority

Right Turn from Dedicated BRT Lane - Monterrey, MX

The EMTRAC system enhances the following "essential features that define BRT"[2]without requiring additional hardware:

Dedicated Right-of-Way and Busway Alignment: EMTRAC-equipped vehicles are able to automatically open entrance gates to dedicated BRT lanes.

Off-Board Fare Collection: Vehicles may request signal priority at near-side stops (depending on door status) or while approaching far-side stops (depending on stop-request status).

Intersection treatments: In addition to signal priority, precision vehicle detection allows for lane-specific actuated phasing.

Platform-Level Boarding: Account for faster loading times by customizing the conditions under which priority is requested. As a result, signal phases are not altered until necessary.

Transit agencies are also able to monitor real-time BRT activity with the EMTRAC Central Monitor system.

  • Industry-best satellite and inertial positioning enables vehicles to request signal priority by lane.
  • Equipped vehicles can automatically open busway and garage entrance gates, without requiring additional onboard hardware.
  • Route timepoints may be automatically reported by vehicle, with timepoint data saved to detailed activity logs.
  • Central Monitor software displays vehicle activity in real time on interactive map.
  • Vehicles are easily configured to allow signal priority only under specified conditions.
  • Timeliness: Vehicles behind schedule may be configured to continue requesting signal priority until they are back on schedule.
  • Ease of Installation: EMTRAC BRT equipment is the same as used for other EMTRAC applications.
  • Expandability: Agencies can upgrade their existing EMTRAC system with minimal effort, adding capabilities as schedules and budgets allow.
  • Flexibility: Install additional components for specific vehicles (or vehicle classes). For example, install EMTRAC Control Heads (to provide driver alerts) only on rapid-transit buses.
  • Accuracy: The EMTRAC system utilizes the most precise vehicle-position technology to ensure exact location reporting—even in unfavorable urban environments.
  • Security: Frequency-Hopping Spread Spectrum radio signal has superior range and utilizes AES encryption.

Information Sheets


The EMTRAC Central Monitoring System enables supervisory personnel to remotely monitor bus activity and progress in real time.

Transit Control Center with EMTRAC Central Monitor - Automatic Vehicle Location System

EMTRAC Central Monitor Displaying AVL Maps

With EMTRAC AVL (automatic vehicle location), equipped buses automatically transmit location and activity data to network-connected EMTRAC detectors in wayside cabinets. This data is displayed on central workstation monitors, showing vehicle movement on a map in real-time. It is also recorded in detailed logs for later review.

The components used for this system are the same as those used for basic EMTRAC EVP/TSP functionality, making it both a simple and cost-effective way to implement an accurate and reliable AVL system.

  • Automatically locate specific buses and intersections with the click of a mouse.
  • Connect to intersection controller switches to enable display of current signal status on map.
  • Automatically download and save activity logs from onboard VCUs while vehicles are parked at garages.
  • Configure system to automatically generate reports, which are automatically emailed and archived at specified intervals.
  • Automatically alert designated personnel—as specified events occur or on a daily/weekly basis.
  • Verify proper system functionality by monitoring signal-controller responses to priority requests.
  • View logs and generate reports that show changes in connectivity status to help identify possible network issues.
  • Timeliness: Improve schedule adherence and maintain headway by requesting signal priority when agency-specified conditions are met.
  • Ease of Installation: Central Monitoring System interfaces with existing EMTRAC TSP and EVP system components, requiring minimal additional equipment.
  • Expandability: Agencies can upgrade their existing EMTRAC systems with minimal effort, expanding the system as schedules and budgets allow.
  • Flexibility: Customize detection zones for specific vehicle classes, and define the conditions under which TSP requests are transmitted.
  • Accuracy: The EMTRAC system utilizes precision satellite and inertial positioning to ensure exact vehicle location reporting—even in unfavorable urban environments.
  • Security: Frequency-Hopping Spread Spectrum radio signal has superior range and utilizes AES encryption.

Information Sheets

GNSS Data Analytics

EMTRAC Conditional Transit Bus Priority

Example of Data Analytics System Report

The EMTRAC Data Analytics system enables transit agencies to evaluate numerous vehicle and intersection statistics in a graphical format—making it easy to recognize route and ridership trends, improve controller timing, and determine answers to common TSP questions such as:

  • Is the system functioning properly, and how can it be improved?
  • What are the impacts on other road users?
  • How often is the system active?
  • Does the system meet performance targets?
  • Where should check-in and check-out points be located?

What is GNSS Data Analytics?

The EMTRAC components calculate precise vehicle position on a frequently recurring basis, while also storing detailed logs of vehicle and intersection states. The massive amount of resulting data is utilized to generate a variety of detailed graphs and reports. These reports accurately show trends by time and day of the week, routes and corridors, intersection, bus stop, timepoint, or nearly any other data set. Data provided by EMTRAC enables transit priority system improvements to be critically evaluated before implementation—allowing more accurate projected results.

Transit-system improvements from using EMTRAC Data Analytics are often made without requiring additional hardware installations.

Automatic Logs & Updates

The EMTRAC Interrogator System enables transit agencies to automatically download activity logs from—and upload firmware and database updates to—equipped vehicles.

EMTRAC Interrogator System - Download TSP Activity Logs

Automatic Transfer of Activity Logs at Bus Garage

The EMTRAC Interrogator System can be used at bus garages, rail operations centers, maintenance facilities, as well as other locations.

As equipped vehicles return to garages, the EMTRAC Interrogator System utilizes secure frequency-hopping spread spectrum radio to download activity logs from onboard EMTRAC units. This data is forwarded to a server running the EMTRAC Central Monitor software, where the data may be viewed by authorized personnel.

  • Automatic Retrieval and Update: Wirelessly download activity logs from EMTRAC components, and automatically upload firmware or database updates to units that have not yet received the update.
  • Auto-Notifications: The EMTRAC software may be configured to email periodic activity logs to specified agency personnel.
  • System Monitoring: The EMTRAC software enables agency personnel to monitor connection status and history (between server and Interrogator as well as between Interrogator and EMTRAC components), and current RF signal strength.
  • Communication Stability: Data is not lost in cases of network interruption, and data transfers resume from the point of interruption.
  • Low Profile: For external connections, the EMTRAC Interrogator Kit requires only 120 VAC power and Ethernet. All communication with EMTRAC vehicle components is performed wirelessly.
  • Limitless Memory: By transferring activity logs to the system server, onboard EMTRAC components are able to continually store new log entries.
  • Timeliness: High communication rates enable fast data transfers, while offering many options for where to mount the Interrogator—such as near refueling or washing stations.
  • Flexibility: The EMTRAC Interrogator may be mounted on wall, pole, or other structure, and multiple antenna options allow for reliable communication, even in high-interference environments.

Information Sheets

Rail Transit

Transit Rail Station

Transit rail vehicles are also able to utilize the EMTRAC system to enhance schedule efficiency and improve safety. In addition to signal priority, equipped agencies are able to implement key Positive Train Control (PTC) functions, including Overspeed Protection, Collision Avoidance, Wayside Worker Alerts, and Stop-Bar Overrun Alertsusing standard EMTRAC equipment.

For more detailed information about EMTRAC for rail transit, please visit EMTRAC Rail.


  1. Wright, Lloyd, and Walter Hook. The BRT Planning Guide. New York: Institute for Transportation and Development Policy, 2007.
  2. "What Is BRT?" Institute for Transportation and Development Policy. ITDP, Web. 6 Aug. 2015.
  3. Baker, Ronald J., et al. An Overview of Transit Signal Priority. Ed. James Chang. Washington, DC: Intelligent Transportation Society of America. 2004. ITS America.