Ambulance

Focus on Global Traffic Technologies
Seeing the Lights: the Traffic Signal
Technology that can Save Time and Lives
Tim Hall, market and development director at Global Traffic Technologies, looks at the
history and technology behind the traffic systems that allow ambulances to respond to
incidents more swiftly and safely
When an emergency vehicle arrives at a
traffic intersection, sirens blaring and lights
flashing, the result can be a frightening
disruption.
Drivers suddenly realise they need
to manoeuvre their cars to allow the
emergency vehicle through. Some drivers
panic, becoming confused and creating
conflicts that can cause blocked lanes and
emergency vehicle crashes, increasing
response times.
But intelligent transportation technologies
that provide emergency vehicles with
a green light at intersections can help
minimise driver confusion, reduce collisions,
and improve emergency response times.
This is an emergency vehicle preemption
system, or EVP. EVP systems are designed
to give emergency vehicles a green light
on their approach to an intersection
while providing a red light to conflicting
approaches.
EVP systems are a simple but powerful
solution that can rapidly and dramatically
improve safety and response times.
History of priority control systems
Both Europe and North America adopted
traffic light priority control in the 1960s, but
developed the technology in contrasting
directions.
In North America, the first users of priority
control were emergency services, including
fire, police and ambulance companies. Public
transport agencies did not take up the
technology until the mid-1970s. In Europe,
conversely, the public transport segment was
the early adopter, followed by emergency
service users.
One reason for the difference is that in
North America local police and fire chiefs
controlled the procurement budgets
for their agencies and were interested
in supporting a dedicated EVP signalling
system approach. Agencies in Europe at the
time had a stronger focus on mass transit
priority control using existing loop-based
vehicle detection systems. These systems,
however, were not suitable for emergency
vehicle use.
Another factor that may have delayed
widespread introduction of emergency
vehicle priority systems in the European
region was the technology used to signal a
preemption request to the intersection.
At that time the most popular methods
being used were strobe lamps, centrally
activated green-corridors and sound
based signalling. In North America the
stroboscopic system emerged as the
dominant technology. Sound-based systems
had inconsistent performance, and there
Similar technology is used for transit signal
priority systems, which enable public
transport agencies to extend or truncate
green cycle times at traffic signals for more
accurate schedule adherence. This means
public transport vehicles — including buses,
light rail trains, street cars, cable cars and
trams — spend less time waiting, lowering
fuel and fleet costs and reducing carbon
emissions.
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64 Spring 2016 | Ambulancetoday