Traffic speeds and volumes  for Gateway are determined using speed sensors. These sensors, either in the pavement or mounted along the roadway help monitor the flow of traffic and traffic speeds in all lanes of the roadway.

These sensors help monitor the speeds on the interstates and arterial roadways and provide automated alerts to MoDOT Transportation Management Center staff when traffic speeds significantly dip along those routes.  This can indicate a roadway incident -- debris on the road, a crash or stalled vehicle, or some other situation that is impacting traffic.  Operators can then check the live camera views to see what the incidents is, and direct the appropriate emergency response forces -- law enforcement, fire department, MoDOT maintenance or emergency operators -- to the site to address the incident and help get traffic moving smoothly again.

Information on traffic speeds is also shared on MoDOT's Traveler Information Map across the state, based on information obtained from these sensors. Drivers can also check traffic speeds along those monitored routes on the MoDOT Traveler Information Map. This information can help them better plan routes they want to use for their commutes, or other travel around the St. Louis region. Traffic is rated as green (moving at least 45 mph), yellow (moving between 31 and 45 mph) and red (moving at 30 mph or slower).