Transcript Delineation, signing and lighting

Delineation, signing and
lighting
Time Spent: 8 hrs
Hossein Naraghi
CE 590 Special Topics
Safety
March 2003
1
Delineation
 Delineation
 Roadway
delineation is used to
•Control placement and movement of
vehicles
• providing information to the driver that
identifies the safe and legal limits of the
roadway
•Regulate direction of travel, lane
changing and overtaking
2
Delineation (continued)
•Mark lanes or zones
• to show turns or parking are permitted,
required or restricted
•Improve lane discipline
• Particularly during night time driving
•Aid in identifying potential hazardous
situations
• e.g. obstacles and pedestrian crossing

Delineation is of critical importance to
the safe and efficient operation of the
road system
3
Delineation (continued)


Delineation is vital in enabling the driver to
locate the vehicle on the roadway and to
make navigation and control decision
Short range delineation


Enables the driver to keep the vehicle within the
traffic lane
Long range delineation



Plan the immediate forward route driving task
Needs to be consistent and continuous
Not restricted to locations where forward
visibility is confusing or critical
4
Delineation (continued)
The curve characteristics of direction
may need to be assessed up to 9
seconds ahead
 Detailed tracking data for actual curve
negotiation may be required 3 seconds
ahead of the curve
 Delineation is much more critical for
older drivers

• Due to the reduced visual capability, rely to
a greater extent on correct delineation of
the road ahead
5
Delineation (continued)

Delineation devices fall into two
groups
Pavement markings
 Roadside device


Pavement markings

Usually applied using
• Paint
• Thermoplastic material

Should be highly reflective
• e.g. use of glass beads mixed into the paint
6
Delineation (continued)
Need to be skid-resistant
 Should be durable
 Massage they convey must be clear and
not led to confusion
 Massage must be simple and clearly
understood


There are three categories of pavement
markings

Longitudinal lines
• Centerlines, lane lines, edge lines, barrier lines
7
Delineation (continued)

Transverse lines
• Stop lines at intersections
• Pedestrian crossing lines

Word and symbol markings
• Pavement arrows
• Painted channelization

It is common in UK to use

pavement marking to indicate which lane
the driver should be in for a particular exit
from an intersection
8
Delineation (continued)




Zig-zag lines to indicate the approach to
pedestrian crossing
Yellow box markings to indicate extremities
of signalized intersection
Speed limit painted on the road surface
Limited usefulness of word and symbol
marking

Adverse condition
• At night, in the wet, and under heavy traffic

Such marking may lead to skidding
9
Delineation (continued)

Lane lines and edge lines are particularly
helpful in condition of poor visibility
• At night, in fog or rain

Edge lines sometimes provided at the
outside edge of the roadway
• Give marginal advantage in driving
performance
• Main advantage is in short term lane
positioning
• Are as effective on straight alignments as on
curves
10
Delineation (continued)

Delineation of the outside age of
roadway is highly desirable
Especially for roads wider than 6 m
 Evidence shows delineation provides
important guidance to motorist

• When visibility decreases due to adverse weather
or night time condition

Various studies show safety benefits of edge
lines
• Jackson (1981)reported reduction in total crashes
between 13 to 30% and reduction of 37- 42% at
11
night following installation of edge lines
Delineation (continued)
• Tignor (1993) reported a 2% reduction in total
crashes and 25% run-of-road crashes in US
• Another Study in US by Russell indicated that
edge line can be justified on two-lane rural
roads if there is an average of one nonintersection crash annually per 15.5 miles

Other studies questioned the usefulness of
edge lines
• UK county Surveyors’ Society 1989 found that
edge line was effective only when it was used
at site with specific problem involving loss of
control
12
Delineation (continued)

Edge lines are usually 4 inch or 6 inches
Studies show 6 inches edge lines are
more effective especially on curves
 A study in US by Lum and Hughes (1990)
found that Using 8 inches edge lines can
be cost-effective where

• Pavement width exceeds 24 ft
• Shoulders are unpaved
• Traffic volumes exceed 2000 vpd
13
Delineation (continued)

Raised reflective pavement markers
Present a reflective face to oncoming traffic
 Provide better night time delineation than
painted center lines and edge lines
especially under adverse weather condition
 Moses (1985) reported the effect of
installation of RRPM’s on sections of rural
road in Australia

• Reduction from 33 to 10 head-on crashes
• Reduction from 29 to 4 sideswipes crashes
14
Delineation (continued)

Rumble devices
Grooves or raised ridges placed on
roadway to provide a sudden audible and
tactile warning to the driver
 Two types

• Longitudinal installation to counter driver
fatigue or inattention
• Use on shoulder, edge line, center line
• Transverse installation to alert drivers to an
impending feature
• Approach to an intersection
15
Delineation (continued)
• Approach to toll plaza
• A speed limit change
• A horizontal curve
• A lane drop
• Approach to work zone

A number of designs have been used for
longitudinal installations
• Markings are
• highly reflective
• Thicker than paints
• Lines are easily visible above road water on wet days
16
Delineation (continued)
• Have a longer life than painted lines
• Raised reflective pavement markers give a tactile
sensation when a wheel runs over them which
may contribute toward their safety effectiveness
• Profile edge lines include thermoplastic
material applied
• As continuous extrusion with raised transverse
bars
• As separate transverse bars laid directly on the
pavement
• As a series of parallel grooves passed into the
shoulder
17
Delineation (continued)

Harwood (1993) cautioned against overuse of rumble devices
• They may loose their ability to gain the motorist
attention

One study on effectiveness of rumble strips
on the approach to 52 narrow bridges on
two highway in Oklahoma shows
• Over a four year period, the number of run-ofroad crashes per million crossing vehicles at the
test site fell by 35% on one and 47% on the
other
• Fatal and injury crashes fell by 52% and 56%
18
Delineation (continued)

Roadside devices include

Continuous devices
• Guide posts

Devices used only at discrete sites
• Bends
• Chevrons
• Bridges
• Guardrails
19
Delineation (continued)

Guideposts and post mounted delineators

Guide posts are
• light weight
• 3-4 ft high
• Located 2-10 ft from the edge of the outside lane
• Should be
•
•
•
•
•
•
Low cost
Easy to transport
Cheap to install and replace
Resistant to extreme weather condition
Present no safety hazard to road users
Present no psychological obstacle to road users
20
Delineation (continued)

Guide posts usually have a reflective
device attached
• referred to as a post-mounted delineator
• Assist long range delineation at night
• Made from reflective sheeting or from
moulded plastic using corner cube principle
• Should be designed to ensure visibility at
long distances, especially at night
• Be high enough to avoid being soiled by mud
21
Delineation (continued)

Some studies reflect the effectiveness of
guide posts with reflective delineators



30% reduction in crashes when installed on
curves on two lane roads in US
67% reduction in crashes when installed on
undivided roads in UK
A study on a two-lane rural roads with a 50
mph speed limit found that the reflector
posts led to an increase night time average
speed of 3 mph and an increase of 20% in
crashes
22
Delineation (continued)

Chevrons
Delineation is critical on curves with
radius less than 2000 ft
 Chevrons commonly used to warn
drivers of

• Sharp bends
• Medians
• islands
23
Delineation (continued)

Curve alignment markers (CAM)
A single post mounted chevron
 Highly contrasting colors

• Black on yellow
• Red on yellow

Bhatnagar (1994) developed a relationship
between approach speed and curve advisory
which indicate that CAMs are suited where
there is a difference between these two speeds
of about 20 km/h, with CAM’s spaced at:
24
Delineation (continued)
• 0.12R + 4 meters (for V<80 km/h)
• 0.08R + 2 meters (for V>80 km/h)
Where V is the approach speed (km/h)
R is the curve radius (m)

Bhatnagar importantly recommends that the
use of CAMs should be reserved exclusively
for curve delineation and NOT use for
• Roundabouts
• Pedestrian refuges
• Bull nose of guardrails and etc
Since such practices will reduce the
effectiveness in more critical curve delineation
25
Delineation (continued)

Object markers

Are applied to hazards such as
•
•
•
•
•
•
•

Bridge abutments
Underpass piers
Handrails
Culverts
Trees
Poles
Bridge piers
No known studies have been conducted to
determine the effectiveness of specific object
markers
26
Delineation (continued)

Variable message signs
Speed-activated ‘too fast’ signs reduced
crashes at sharp curves in Canada
 A range of dynamic aids which were
tested at bridge sites included

• Flashing beacons
• Actuated flashing strobes
• Actuated narrow bridge
• Oncoming
27
Road signs

Road signs are of three types

Regulatory signs
• Speed limits
• Parking restrictions
• Direction of traffic flow
• Turn controls
• Stop or yield

Warning signs
• Alert the driver to potential hazards ahead
• Intersections, curves, crests, pedestrian crossings
28
Road signs (continued)

Information signs
• Give drivers information about route direction
• Destinations
• Tourist facilities
• Services

Sign maintenance
• Signs will remain functional and achieve their
safety objectives if adequately maintained
• They fade under sunlight, are subject to
accidental and vandal damage
29
Road signs (continued)

All signs should be subject to regular
maintenance and inspection to ensure
• They have not become obscured by foliage or
other roadside installations
• Each sign is in good physical condition
• Each sign is performing its function and
conveying its message in day and night
• Sign’s function is still relevant and necessary,
and there is no need to update or replace it
• All signs and markings are cleaned sufficiently
• Supporting structures are in sound condition
30
Street lighting




Street lighting of appropriate standard
contributes to road safety in urban areas
It is particularly important where there are
pedestrians and cyclists
In rural areas, lighting of isolated grade
intersections can be a worthwhile safety
benefits
It should be also noted that the safety
benefits of improved lighting can be offset to
an extent if lighting posts are poorly located

A high proportion of urban single vehicle crashes
31
involve utility poles