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Delineation, signing and lighting

Hossein Naraghi

CE 590 Special Topics

Safety

March 2003

Time Spent: 8 hrs

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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

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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

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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

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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

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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

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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

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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

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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

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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

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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 night following installation of edge lines

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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 non-intersection 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

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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

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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

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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

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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

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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

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Delineation (continued) Harwood (1993) cautioned against over-use

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-of-

road 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%

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Delineation (continued) Roadside devices include

Continuous devices• Guide posts

Devices used only at discrete sites• Bends

• Chevrons

• Bridges• Guardrails

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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

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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

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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

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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

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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:

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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

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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

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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

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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

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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

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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

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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

involve utility poles