Pioneering vehicle-to-infrastructure technology drives safety in Tampa

Siemens Mobility roadside units communicate real-time, high-speed traffic information to connected vehicles.

RSUs enable rapid decisions that prevent collisions

Downtown Tampa is significantly safer today thanks to connected vehicles (CVs) that make decisions about traffic conditions 10 times a second. The CVs are acting on real-time, high-speed communication from Siemens Mobility pioneering roadside units (RSUs). The Tampa Hillsborough Expressway Authority (THEA) selected Siemens Mobility turnkey CV solution when it received one of three awards from the US Department of Transportation (USDOT) in 2015 to test CV technology.


The RSUs are the central infrastructure gateway that allows two-way communication between Tampa’s intelligent traffic system and the 1,500 vehicles equipped with connected vehicle technology. More than 40 RSUs are located at key points throughout downtown Tampa, including the on and off ramps for the expressway and the reversible express lane. The RSUs interact with a system of physical roadside detectors so they can collect the information that prevents collisions between cars and with vulnerable road users such as pedestrians and cyclists. The RSUs relay the information to the CVs using direct short-range communication or DSRC.


The Tampa pilot project is one of the first in the U.S. to deploy connected vehicle technology in a downtown urban area. Siemens Mobility continues to develop new applications that make CV technology even more effective in preventing crashes by unimpaired drivers.

Applications generate immediate warnings

Siemens Mobility applications interpret the information from roadside detectors to make it useful for the CVs. The information is turned into a variety of warnings as well as signal status and travel time updates, all of which are displayed on the CV’s rear-view mirror or communicated through sound alerts. The alerts include:

  • Pedestrian collision warning (PCW)
  • Wrong-way entry (WWE)
  • Forward collision warning (FCW)
  • Emergency electronic brake light (EEBL)
  • Transit signal priority (TSP)
  • Red light violation warning (RLV)
  • Exit ramp deceleration warning (ERDW)
  • Emergency vehicle preemption
  • Variable speed limit
  • Curve speed warning (CSW)
  • Wi-Fi/Bluetooth travel time
  • Do not pass warning
  • Vehicle turning
  • Intersection movement assist (IMA)
  • Work zone warning
  • Reversible express lane status
  • Signal phase and timing countdown (SPaT)

Real-time information reduces congestion and emissions

The real-time information sent by the RSUs also helps relieve congestion in downtown Tampa. For example, signal phase and timing countdown (SPaT) is used to display the time remaining on a green light on the rear-view mirror. The driver can adjust the approach speed to catch the green signal and avoid unnecessary stops. Likewise, it sends a warning if the driver is about to run a red light. Downtown Tampa also features a reversible express lane that has a curved exit. RSU information improves traffic movement through the lane by reducing peak-hour queues. Keeping traffic flowing reduces greenhouse gas emissions.