If the Speed Zone is Ineffective
If the majority of motorists are disregarding the speed
zone it is an indication that something is ineffective with the traffic control plan and
reassessment of the traffic control plan is necessary. In relation to speed, look for the
following:
Conflicting Messages – this occurs when trying
to reduce motorists’ speed in an area that encourages motorists to increase their
speed. Such as; passing lanes or areas of road that are spacious and "visually
open" or curve warning tabs that show a speed higher than the work zone speed limit.
Inappropriate Speed Zone – this could be a
speed that is either too fast or too slow for the work activity. Both have the same result
– the motorist approaches the active work site too fast for the conditions. An
appropriate speed zone should result in the majority of traffic moving in an effective and
efficient manner with few aggressive or evasive maneuvers.
Too Slow:
Many people feel "slower is safer". This is
not always the case when referring to speed zones. When developing the traffic control
plan it is essential that motorists’ perception of the traffic pattern change is
considered.
Studies have demonstrated that motorists will typically
alter their normal driving pattern and follow temporary traffic signing for approximately
12 –15 seconds. However, after this time, they will resume normal driving patterns if
they do not encounter justification for that change.
This means that motorists will begin to speed up if the
work zone does not justify the reduced speed. This creates a hazard to workers as they
expect motorists to be travelling slower than actuality. This also creates a hazard to
motorists as it creates differentials in speed from one motorist to another – some
will always follow the posted speed limit and others will drive at a comfortable speed
depending on the surrounding factors.
Other negative motorist responses to excessively slow
temporary speed zones (typically in advance of the active work site) are aggressive
displays such as:
- passing in work zones and other unsafe areas
- tail gating,
- a general disregard for temporary traffic control devices
and speed zones.
The result is that the motorist has sped up between the
advance signing and the active work site and will enter the work site too fast. The driver
will then have to perform evasive maneuvers (e.g. heavy braking) within the active work
area.
Too Fast:
Speed zones that are too fast for the traffic pattern
change also pose substantial hazard to motorists and workers. There will be fewer
aggressive type symptoms as described in the "Too Slow" section in advance of
the active work site; however, similar symptoms will occur at the active work site as a
result motorists approaching too quickly. Look for:
- heavy braking and evasive maneuvers as a result of
inadequate perception reaction or stopping distance,
- speed differentials (as some drivers slow down and others
don’t), and
- confusion due to information overload – too many
messages over a short period of time.
Site Layout – The speed may be
affected by site factors such as curves or hills in which motorists need more warning in
order to react or in which commercial vehicles need a run to climb a hill.
Length of Speed Zone –
Motorists will reduce their speed for approximately 12 –15 seconds. If they do not
encounter the active work area, traffic queue or other justification for the reduced speed
within this time, they will resume their original driving pattern.
Unnecessary Speed Zones –
Reduced speed zones must be removed or covered when not justified. If a reduced speed zone
has been left posted while the site is inactive, such as weekends, evenings, etc. then the
signs lose effectiveness with repeat traffic. This loss in effectiveness is carried from
one project to another.
For further information on speed zones and traffic control
plans, refer to the "Fundamental Principles" section of the Traffic Control
Manual for Work on Roadways.
Prior to performing work on
roadways, contact the Ministry of Transportation District Office for local policies and
traffic information.
Shanna Mason
Ministry of Transportation
Human Resources Branch
Health and Safety Section
August 2001
|
