Traffic Engineering Pilot Initiatives

Page updated on August 9, 2022 at 8:51 AM
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Why Pilots?

 

Being forward thinking and innovative are guiding principles of the Smart Mobility Program.   With emerging technology that changes constantly, the City aims to proactively assess new technology solutions to better manage traffic and advance City goals.  Pilots enable staff time to evaluate projects with specific measures to determine success and compare technologies to understand the pros and cons of various vendors.  In addition to pilots, staff actively researches and evaluates vendors and technologies to determine if they might be a good fit for Alexandria. 

 

Ongoing Pilot Projects

  • Duke Street Traffic Mitigation: The City has recently gained access to a platform that helps analyze traffic volumes and patterns.  With this new technology, the City is more equipped to experiment with changes to the roadway to understand how people modify their behavior in response to the changes on the street. The City is working through two pilot projects aimed at reducing regional cut-through traffic on neighborhood streets and shifting traffic onto the major arterials.  To do this, we also must improve the flow of traffic on the arterials and make those routes faster than cutting through the neighborhoods.
  • Hydrogen Fuel Cell Backup Power: The City of Alexandria is the first municipality in the country to implement a hydrogen fuel cell backup power system at a traffic signal.  A hydrogen fuel cell was deployed at the intersection of King Street, Quaker Lane and Braddock Road and is currently being studied.   Traditional backup power is supplied by batteries.  Although batteries have been around a long time, the run time is limited, and the batteries wear out after several years.  Hydrogen never wears out and there are fuel cells that can operate a traffic signal for up to a week.  Hydrogen is expensive to refuel, and the City is evaluating more cost-effective sources of hydrogen. The City will consider future deployments once the high refueling costs  can be overcome.  

  • Battery Backup Power: The City of Alexandria, along with other municipalities, identified evacuation routes where traffic disruption due to signal outage could have a regional impact during emergencies. In 2016, the City was awarded grant funding to equip eleven critical intersections along those routes with Dry Cell Battery Backup Power capabilities to ensure traffic signals would continue to operate during power outages. The city is evaluating the dry cell technology and comparing it to wet cell and fuel cell technology and so far, has been pleased with the size, durability and minimal maintenance required at these locations.  Staff is considering an expansion of this program through future grant opportunities.

  • Video Detection: While inductive loop detectors at intersections have been the most reliable standard for detecting vehicles to trigger signals to turn green or provide a turn arrow, new technology has been improving the reliability of video detection as well as allowing for the detection of cyclist and pedestrians.  Some video can also provide useful data such as vehicle, bicyclist, transit, pedestrian and heavy vehicle volumes.  The City is evaluating and comparing three detection technologies to determine if they are more economical, reliable and provide additional information that can be used to make decisions and better manage traffic. 
  • Digital Subscriber Line (DSL) Communications: The City’s traffic signal communications network has over 30 miles of telephone grade copper communications cable which does not support the bandwidth to transmit high resolution video from CCTV cameras or connect with newer traffic signal equipment.  DSL is being deployed as a temporary technology until fiber optic cable can be installed to bridge this gap.  It has been deployed along portions of Duke Street, where it  is successfully transmitting high resolution video from CCTV cameras to the control center at Business Center Drive.  
  • Passive Optical Network (PON): The cable TV industry developed Passive Optical Network technology to bring fiber to the home.   PON was developed as a more economical architecture than standard fiber topologies. PON is like the outlet strip that desktop computers and peripheral devices are plugged into.  The outlet strip multiplies the number of devices that can be plugged into one electrical outlet.  PON does the same thing with fiber. One fiber can feed multiple fibers using a fiber optic splitter.  The City is one of the first municipalities to deploy this technology on a fiber optic traffic signal network.  Several traffic signals along Duke Street were connected to the traffic fiber optic network using PON technology.  The implementation was a success and another 60 traffic signals are slated to deploy PON through the ITS Integration Phase III project.