Countdown Signal Heads
For Vehicles
Outlines
 Problem Statement
 Hypothesis
 What are the benefits of the countdown timer?
 How would the countdown timer enhance safety ?
 Possible Implementations
 Two types of Countdown Timer Signals
 Comparing the two types of the Countdown Timers
 Discussion
 Would this encourage drivers to speed up and cause even more
accidents?
 Day time and night time
 Other issues..
Problem Statement
 Crash analysis show that a high percentage of crashes,
injuries and fatalities for Drivers, Cyclist and Pedestrians
occur at busy traffic intersections specially the Rear End
and Angle type crashes.
Example: US 440 @ Wake Forest Road. 325 Crashes for the past
three years , 118 crashes is Rear End, and 84 is Angle type.
The percentage of rear end and angle crashes for Wake County
for the past three years is 35.42% and 14.36% respectively.
Problem Statement
 The hesitation that every one of us experience, whenever
we approach an intersection while the yellow light is on,
is a major factor in these fatal collisions. (Should I pass
or stop?)
Hypothesis
 Countdown signals for vehicles would:
Enhance safety at high risk intersections by reducing
angle and rear end type crashes.
Studies show that pedestrian countdown signals
enhanced safety at crosswalks.
Reduce the amount of lost time for each cycle by
reducing the all-red time, and therefore increase
capacity.
How does the Countdown Timer
enhances safety?
 Countdown signals would provide visual information and
guidance to drivers regarding the amount of time remaining
to safely cross an intersection.
 Attracts drivers’ attention to the yellow light by visualizing,
rather than guessing, how many seconds left for them to
slow down and stop safely before the red light turns on.
 Caution aggressive drivers while approaching an
intersection to slow down when they see a timer instead of a
solid yellow light. That would reduce red light runner
drivers.
Two Types of Countdown Signals
Countdown signal head as a separate unit.
Countdown timer inside the yellow circular ball.
First Proposed Implementation
Countdown signal head as a
separate unit.
Installed as a rectangular screen
that can display big enough digital
numbers.
It works along with the yellow
light interval.
This can cost around $1000 plus
maintenance.
43120
Second Proposed Implementation
Countdown signal timer will display
digital yellow color number surrounded
with a yellow circular boundary.
Three options for the possibility of what
time interval can these numbers
represents:
Each number can represent one second
interval.
Each number can represent increment of
a second like each digital number can
represent half second period or each two
numbers is equal to one second interval.
Each number can represent two seconds
intervals.
Comparing the two types of
Countdown Timers
The rectangular screen
installed above the traffic
signal.
Improving the solid yellow
light to circular boundary
with numbers in the middle.
 Numbers are big enough to read from a
distance.
 Numbers will be much smaller and hard
to read from a distance, however the first
couple drivers approaching the
intersection will be able to read them.
 Costs less, as we are only improving the
traffic controller itself and maintenance
will be the same as the present controller.
 Easy to understand for most drivers.
 Costs more (Installation and maintenance).
 maybe hard for some drivers to find the
correlation between the timer and the
yellow light.
 If the timer shuts down for any reason we
still have the signal working but if both
were shut down so that can happen even
without timer installed.
 Still following the MUTDC regulations by
keeping the circular yellow shape light.
Discussions
Would this encourage drivers to speed up and cause even
more accidents?
 First we are not talking here about the drivers who would want to break the
law anyway whether there is countdown timer or not.
 A considerable portion of drivers in the dilemma zone will proceed when
they observe the traffic signal changing to red. (High speed, Low reaction
time, variable deceleration rate).
 Worst case scenario;
 An aggressive driver approaching intersection while yellow timer is on
 Timer just changed from two to one
 Driver is in the dilemma zone, pressed on gas trying to speed up and
cross the intersection before it turns red
 He thinks that he has only one second left
 In reality he has two seconds to pass the stop bar and cross the
intersection plus 2 second of all red time…..
 Can you think about a worse case scenario?
Discussions
Day time and night time
How do think this timer will be effective at night time
when visibility is much less and numbers could be hard to
read?
 We can program the timer for a daytime and a night time setting.
From 10:00 PM to 6:00 AM the solid yellow light can be displayed
instead of the numbers.
Questions that might come across
our minds
 What if a truck blocked the view and the driver behind
the truck is no able to see the timer?  can happen in
both cases timer or no timer.
 What if the people get used to see the timer and the
timer shut down for some time?  stop sign as usual
 What attracts you more regular sign on highway or
digital screen that displays the speed limit?  not sure.
But according to some drivers I surveyed, they stated
that it is very helpful to know when the green light will
turn on after the pedestrian countdown is off, and
therefore they though that countdown timers for
vehicles would be as useful.
Thank you for your time and attention..