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Actuation : Manual Operation : Fixed
Time Operation : Timings : Setting
up |
Temporary Traffic
Lights
The Department of Transport
Roads and Regions advise that temporary traffic lights are
used on vehicle actuation (VA) mode unless permission to use
them on any other mode is authorised by the street authority
or in the event of a malfunction or emergency.
Where temporary traffic lights
are to be used in the proximity of rail crossings they must
not straddle the crossing or be used within 50 metres of
them. where there is a risk of tailbacks the lights must be
operated manually. Rail Track advise the use of Stop/Go to
control traffic in the proximity of level crossings.
To work efficiently the traffic
lights must be tested before setting up and daily there
after, they must carry the DETR approval plate and set up
correctly. The site length must not exceed 300 metres as the
ALL RED period will not allow
the shuttle lane to empty before the opposite end changes.
Vehicle
Actuation
This method of
operation is aimed at reducing delays to traffic by using
microwave vehicle detectors to detect the approach of
traffic and 'trip' the lights to green on demand. The
detectors only detect objects moving towards them at speeds
of about 5mph or more, they do not work by flashing car head
lights at them as is often thought. To work efficiently the
detectors must be pointed towards the approaching traffic
with no obstructions blocking the them. The detectors can
detect traffic up to 70 metres away. The default minimum
green period is 12 seconds which will allow a vehicle
approaching the lights to have sufficient time to enter the
shuttle lane before returning to red. In the absence of
traffic the lights will stay on red at each end. Some
systems have a default time built into the system where the
lights will go through the sequence of changing if there has
been no activity to trip them, just in case a slow moving
vehicle has approached the lights.
Manual
Operation
This mode should only be used
to relieve short term difficulties when traffic is
particularly heavy from one approach or to clear/prevent
tail backs. Manual operation must be used where there is a
risk of tail backs to junctions, roundabouts, rail
crossings, etc. The operator must always set the ALL
RED period timings as determined by the distance
between the 'wait here' signs.
Fixed Time
Fixed time operation should
only be used in the event of a failure with the vehicle
detectors. Using fixed time to operate traffic signals will
lead to traffic delays and tailbacks when traffic is heavy
or flows mostly from one direction.
Signal
Timings
The signal timings are
adjusted to suit the site length measured between the 'wait
here' signs. Timings can be adjusted where the ALL
RED period is too short to allow traffic to clear the
shuttle lane by increasing the red settings, or to allow
more traffic to go through the site from the busy end by
increasing the MAXIMUM GREEN
settings. Due to the limitations on the ALL
RED timings the maximum site length should not exceed
300 metres. See below for timings.
RED
TIMINGS (seconds)
Site length measured
between the 'WAIT HERE' signs (metres) |
| 0 - 50 |
50 - 100 |
100 -
150 |
150 -
200 |
200 -250 |
250 -
300 |
| 5 |
10 |
15 |
20 |
25 |
30 |
MAXIMUM
GREEN TIMINGS (seconds)
Site length measured
between the 'WAIT HERE' signs (metres) |
| 30 - 75 |
75 - 135 |
135 -
195 |
195 -
300 |
| 35 |
40 |
45 |
50 |
Setting
up the Site
Great care should be
taken when setting the site up to minimise the risk of
accidents. Management must carry out a suitable and
sufficient assessment of the risks associated with the site
and site operations. Traffic lights may be set up on the
same side of the road where traffic lanes are restricted or
visibility through the site restricted (Layout 9 Chapter 8).
A logical sequence should be followed when setting out the
site, a suggested sequence is given below. Always face
traffic when setting up the site.
- Place the roadwork's
ahead sign at each end of the site in accordance with
the distances given in the 'Blue Book' and the road
narrows including supplementary plate to show single
file traffic.
- Where
there is sufficient width to allow two way traffic place
a direction arrow at each end of the intended safety
zone and cone off between them to allow a safe working
space that maintains two way traffic flow of at least
5.5 metres for cars and light vehicles or 6.75 metres on
bus/LGV routes.
- Place
the 'traffic signals ahead' and 'wait here' signs ready
to turn to traffic. Facing them to traffic for too long
before facing the traffic signal to traffic may cause
confusion.
- Set
up the traffic lights in the working area, test them,
set the timings and place then on 'HOLD
ALL RED' ready to turn to traffic. Ensure that
cables are not causing a hazard to pedestrians. Where
traffic lights are to be placed on each side of the road
use a cable protector.
- Set
up the 'traffic lights ahead' and 'wait here' signs. The
wait here signs should be placed 2 - 5 metres away from
the traffic signals on the obstructed side of the road
and far enough away on the unobstructed side to allow
traffic to exit the shuttle lane.
- Wait
for a gap in traffic and turn the lights to face
traffic. Traffic should stop at the 'wait here' signs.
- Move
the cones out into the road to construct the shuttle
lane and safety zone with tapers set out a 45 degrees to
the carriageway edge and cones at 1.2 metres maximum
spacing. The cones on the longitudinal should be no more
than 9 metres apart and the shuttle lane width to a
maximum of 3.7 metres (absolute minimum of 2.5m for cars
and 3m for LGV's). If necessary move the traffic lights
to a more suitable position.
- When the shuttle lane
is clear and operatives away from the sideways clearance
turn the controller to vehicle actuation, which will
cause the light to go through the sequence. Watch the
flow of traffic to ensure the lights are working
effectively, adjust if necessary.
Notes:
- The above method is
only one example of setting up the site, each site must
be assessed to determine any special needs.
- Sites with traffic
speeds of 50mph or more will require a 'lane closed'
traffic barrier placed at the end of the lead in taper.
- Where traffic signals
are used on the same side of the road there is the risk
that the detectors will be blocked by high sided
vehicles.
- The site supervisor
must consult with the street authority prior to using
traffic signals.
- Also see TA
63/97
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