bfc 32302 revision final

8/12/2019 Bfc 32302 Revision Final

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Can I Help You ?

Traffic & Road Safety Engineering

Final Revision
http://www.consumerhealthreview.org/brain-health/stress/attachment/stress-2/


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Chapter 4

Traffic Management & Control4.1 TRAFFIC MANAGEMENT

Definitions & Objectives

Reasons for Traffic Management

Problems due to lack of Traffic Management

Traffic Management Techniques

What you will be

learning from this

chapter

4.2 PARKING

Parking Impacts, Policies & Types Parking Studies


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What is Traffic Management?

It is a process of adjusting or adapting the use of existingroad systems to improve traffic operations without resorting tomajor new construction.

What are the objectives of Traffic Management?

The objectives of traffic management are to:

ease traffic congestion

enhance road safety

improve traffic flow

improve the transportation of people and goods

reduce the impacts of traffic on the environment

create a balanced modal split


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Why do we need to manage traffic?

Traffic congestion problem in cities

High urban population growth resultsin the increase of vehicleownership.

The number of private automobilestraveling in cities is high, resulting

in traffic jams.

Conflicts between Private and Publictransport occur.

Traffic jams causes disruptions in Publictransport services.

Passengers are late for work, stressedout, and exposed to fumes, noise and

heat.

Public transport is affected by jams


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Criticisms on new road constructions

Road networks are extended toaccommodate increasing number ofvehicles.

It does not solve the problem oftraffic jams.

It uses up government funds(taxpayers money) and causesscarcity of land.

High energy (fuel) consumption.

Exhaust fumes, heat and noise causespollution and health problems.

Negative impact on the environmentand health


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Mobility, accessibility and safety

problems for non-motorized road usersConflicts between vulnerable roadusers (pedestrians & cyclists) andmotorized transport.

These users find it hard to travel,

access is intruded, and their safetyis at risk.

Cost, in terms of money and time,increases as more time is spent on theroad due to traffic jams.

Increased travel cost


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What problems may occur if traffic is not well managed?

Traffic Congestion

Road AccidentsDisruption of Public Transportation

Adverse effects on Environment

Safety Risk for Pedestrians and Cyclists

Increased Travel Cost

Using up of Funds and Land


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Category Objectives Techniques

Improve Capacity Efficient use of fuel

Reduce time wastage

Promote and develop urbaneconomy

Link & Junctions improvement

On Street parking & trading restrictions

Traffic signals improvement

One way & Tidal flow movements

Roadmarkings and Signing improvements

Allocate Priorities Protect vulnerable road users

Increase effectiveness of highoccupancy vehicles

Pedestrian areas

Cycle lanes

Bus & HOV lanes

Selective detection at signals

Exemption from other regulations

Restraint Improve public amenity

Protect environment

Improve safety

Parking Controls

Physical restraints

Area licensing

Road pricing

Traffic calming

8

TRAFFIC MANAGEMENT TECHNIQUES


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LINK & INTERSECTION IMPROVEMENTS

Use traffic signals

Provide channelizationTo increase capacity

To enhance safetyTo reduce delays

To control speed


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Create safe crossing for pedestrians

Treatment for crossing at anintersection Treatment for crossing at a

midblock

Provide large waiting areas, pedestrian refuges, and shortercrossing distances


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Control speed on the approaches

Neckdowns


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PARKING & LOADING CONTROL

Parking & Loading Restriction

Parking and loading control should be implemented on main trafficroutes, especially during peak hours and near pedestrian movements.

L t D B il D id D i l


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BFC32302 Traff ic Eng ineering and Safety Lecturer: Dr. Basil David Daniel

PARKING & LOADING CONTROL

Benefits of parking & loading restrictions:

Relieves traffic congestionImprove safety

Improves visibility for and of pedestrianswho want to cross

When on-street parking restriction isenforced, provide sufficient off-streetparking spaces.

Designated loading areas must be allocated

for loading activity.

Loading can be permitted only on the backlane, where access is only for goods vehicles.


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ONE-WAY STREET

Advantages:

Reduces conflict points

Increases capacity

Increases speed & flow

Reduces delay

Eliminates head-on collisions

Eliminates dazzle

Easier for pedestrians tocross the road

Proper street signing is very important for one-way streets.


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TURNING & ENTRY RESTRICTIONS

if the road is not able to accommodatelarge volumes of vehicles (No Right-Turn).

if the maneuver is obstructive anddangerous (No U-turn).

if the road or junction geometry is notadequately designed for turning movementsof large vehicles (Light Vehicles Only).

Turning restrictions may be imposed:

for one way street schemesfor certain periods of the day

for certain vehicle classes

Entry restrictions may be imposed:

BFC32302 T ff i E i i d S f t L t D B il D id D i l


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CONTRA FLOW (Tidal Flow / Reverse Flow)

Contra flow is applied when there is an

imbalance in directional distribution oftraffic during peak hours.

Traffic on one direction is in excesswhile traffic on the opposing direction islow.

Justified when 65% or more of the totaltraffic during peak periods is in onedirection.

One lane in the lower volume direction isused for traffic on the higher volumedirection.

This lane is separated using barricadesand channelizing devices and providedwith proper signing.

BFC32302 T ff i E i i d S f t Lecturer: Dr Basil David Daniel


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PEDESTRIAN SEGREGATION

Separate pedestrians from vehiculartraffic.

Objectives:

- To reduce pedestrian-vehicle conflicts

- To enhance pedestrian safety

- To enforce No Jaywalking regulations

Pedestrian Precinct

Pedestrian GuardrailsSidewalk separation using

planting strip


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CYCLIST SEGREGATION

Bicycle Lanes

BFC32302 Traff ic Eng ineering and Safety Lecturer: Dr Basil David Daniel


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BUS & HOV LANES

Bus Lanes

Contra-Flow Bus Lane

With-Flow Bus Lanes

GuidedBus Lane

(Busway)

BFC32302 Traff ic Eng ineering and Safety Lecturer: Dr Basil David Daniel


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BUS & HOV LANES

HOV Lanes

With-flow HOV Lane

Segregated HOVLane

HOV Lane Signages

Contra-flow HOVLane


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BUS PRIORITY

Smart Intersection uses bus detector to manipulate traffic signal

which allows green phase for buses.


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TRAFFIC RESTRAINT

Types of traffic restraint measures:

(1) DO NOTHING

Drivers will eventually make trips during off-peak periods,choose to use alternative routes, and take alternative modesof transport.

(2) PHYSICAL MEASURES

Banning or prohibiting entry of certain classes of vehicles.

Examples: Introduction of Bus & HOV Lanes, Bicycle lanes,

Pedestrian precincts, etc.


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TRAFFIC CALMING

Traffic calming involves changes in street alignment, installation ofbarriers, and other physical measures to reduce traffic speedsand/or cut-through volumes, in the interest of street safety,livability, and other public purposes.

(1) VERTICAL DEFLECTIONS

Speed LumpsSpeed Hump

Speed Bump


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TRAFFIC CALMING

Speed CushionsSpeed Table

Raised Crosswalk

Raised Intersection

Textured pavement

(1) VERTICAL DEFLECTIONS



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g g y

TRAFFIC CALMING

Roundabout

Traffic circle

Chicane

(2) HORIZONTAL DEFLECTIONS


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TRAFFIC CALMING

Neckdown

Central Island Narrowing

Choker

(3) HORIZONTAL NARROWINGS


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CONTROL OVER ACCESSES AND DEVELOPMENT

This is bad planning

Houses have direct access tomainroad.

Future development on the oppositeland will add on to more accesspoints on the mainroad.

Accident risk is high.

This is a better and safer plan

Houses have direct access to a

service road that is connected tothe mainroad.

Future development is located awayfrom the mainroad.

This is a lot safer!


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ENFORCE TRAFFIC LAWS

Traffic law enforcement is meant to

achieve safe and efficient movementof all road users, includingpedestrians.

Stiffer fines and penalties should be

imposed on traffic offenders inorder to prevent repeat offences.

Regular patrols should be made bylaw enforcers.

Road users will learn to respectother road users and become moreresponsible and tolerant.


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SPEED LIMITS AND SPEED ZONES

Speed control can be achieved through

imposing speed limits and implementingspeed zones.

Speed limits should be realistic depending on the road design standard,

road geometry, and type of area.

Speed zones should be introduced atareas with high pedestrian activity, suchas schools.

Enforcement is vital. Road signing,pavement marking, and traffic calming cancomplement these speed limits and speedzones.


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MANAGING HEAVY GOODS VEHICLES (HGV)

HGVs are a nuisance to traffic:

causes damage to road pavement andother road structures

impedes traffic

when involved in an accident, can causeserious injury and damage, or be fatal

HGV operations are not adequatelyregulated.

Vehicles may be defective.

There may be no criteria set for hiring

HGV drivers.Due to long distance travel, drivers maytake alcohol and drugs to stay awake.

Vehicles are grossly overloaded (axleloads of 25-30 tonnes are common).


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Areawide HGV Management Scheme

Prohibition of HGVs from entering orpassing an area or section of a road.

HGV cordons can be used to preventthrough movement while still permittingaccess.

Off-peak Travel for HGVs

HGVs are permitted to use specifiedroutes only during off-peak periods.


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Loading Restriction

Implemented during peak periods to ensure traffic is not impededon major routes. Deliveries and collections can be made early in themorning or late at night.

In pedestrianized areas,they must be done using rear servicingfacilities.


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PROVIDING FOR PUBLIC TRANSPORT

Encouraging the use of public transport is the best solution toreduce congestion (by reducing private automobile usage).

Problems with Public Transport Service:

Inadequate services during peak hours.

Overcrowding.

Delays and inconsistent schedules.

Transit facilities are in deplorablestate.

High fares for poor service.

Journey is too long.

Solution:

Bus Rapid Transit, Busway, Exclusive Bus Lanes, Bus Streets

Light Rail Transit, Monorail, Express Rail Transit, Bullet Train

Improvement of transit facilities


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PROVIDING FOR PUBLIC TRANSPORT

Entry forBus & Taxi Bus Only street Bus Priority

Bus Rapid Transit Inter-modal Transit

Mass Transit


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PARKING (To provide or to restrict?)

It must be recognized that parking demand is always high at a CentralBusiness District (CBD). Time and fuel is wasted, while congestion and

pollution is created by motorists driving around to find parking spaces.Therefore provision of adequate parking spaces is necessary.

Adequate off-street parking facilities (multi-storey car parks, parkinglots, basement parking) should be provided.

But there should be a limit because it may encourage more people to useprivate automobiles.

Illegal parking is rife and often,pedestrian footpaths areencroached.

This, coupled with on-streetparking, creates accident risks forpedestrians as they becomeinconspicuous and are forced untothe roadway.


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PARKING (To provide or to restrict?)

The use of private automobiles can be discouragedthrough:

Parking restrictions

Limiting of parking spaces

High parking fees

High taxes for parking operators

City planners will then have to shift thedemand of parking away from the CBD:

Provide ample parking at mass-transitstations (train & LRT stations)

Provide park-and-ride facilities.

Create satellite car parks.


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THE IMPACTS OF PARKINGAvailability, Convenience and Cost of Parking affects mode choice

PARKING

An owner of a private automobile is likely to use their automobileto access their destination if:

Parking is plentiful

Parking is conveniently located

Cost of parking is reasonable

An owner of a private automobile is NOT likely to use theirautomobile, and choose to use alternative modes if:

Parking is scarce

Parking is inconvenient

Cost of parking is expensive


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THE IMPACTS OF PARKINGParking affects the vitality of communities, commercial and businesscentres, transit systems and airports.

Sufficient parking is important:

when making trips for social visits

to keep businesses alive

to facilitate transport systems buses, trains, LRT & air travel

Parking affects the circulation of traffic in downtown areas

Sufficient parking reduces the time spent by drivers to findparking spaces, hence making traffic flow smoothly

In certain European cities, it was estimated that 40% of thetotal travel time to work was spent on searching for parking!


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PARKING POLICIESTo strike a compromise between the amount of curb space devoted toparking, and for moving vehicles.

To make provision for parking of delivery vehicles, short term parkersand long term parkers.

To design parking lots and their approaches so that street traffic isnot adversely affected by the ingress and egress of parkers.


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PARKING POLICIESTo ensure that the interests of business establishments along thestreet is enhanced by good parking arrangements.

To ensure that parking policies and public transport policies arecomplementary; for example, car parks adjacent to bus stations androutes would enhance bus ridership.


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PARKING POLICIESTo preserve the character of the neighborhood by restricting parkingand enforcing land-use control.

To control parking supply and demand through pricing mechanism;encourage short term parking, and discourage long term parking mayserve to enhance the CBD.


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TYPES OF PARKINGPUBLIC PARKING

On-street parking may be free or not, and it may be regulated orunregulated (e.g. No Parking During Rush Hours, No OvernightParking).

Off-street parking is usually in parking lots, decks (with multi-purpose buildings), or in exclusive parking structures.


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TYPES OF PARKINGPRIVATE PARKING

Usually off-street, private parking includes home or apartmentbuilding garages, stalls, driveways, or affiliate-specific parking(permit required).

For owners of homes and apartments or businesses, and exclusive formembers of clubs.

On-street private parking also can exist.


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Chapter 5

Intersection Design Principles & Control

INTERSECTIONS

Intersection Maneuvers and Conflicts

Priority Intersections

At-grade Intersections

Grade-separated Intersections

Roundabouts

INTERSECTION CONTROL

Design of Traffic Control Signal for Intersections

What you will be

learning from this

chapter


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Number of conflicts at a T-junction

Diverging conflicts - 3

Merging conflicts - 3

Crossing conflicts - 3

Total conflicts 9


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PRIORITY INTERSECTIONMost widely used way of resolving merging and crossing conflicts

Utilizes the STOP and GIVE WAY signsUsed at unsignalized at-grade intersections

Involves a Major road and a Minor road

Sometimes called Major-Minor Junction

Major road is given priority over Minor roadTraffic on Minor road must give way to traffic on Major road

STOP and GIVE WAY signs are positioned on the Minor road

STOP

STOP Line

GIVE WAY

marking

STOP Sign

MAJOR

MINOR


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ROUNDABOUT INTERCHANGE


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ROUNDABOUTSRoundabouts are intersections atwhich traffic enters a one-way

stream around the central island.Roundabouts are a safe and efficientform of traffic control.

They are allowed on local streets,minor and major collectors, minor and

principal arterials, but are limited tono more than two approach lanes.

Some characteristics such as signingand marking can be standardized,while others must be adapted to fit

the demands of the location, such asapproach angles and right of way.

Roundabout operation and safety issensitive to geometric designelements.


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ROUNDABOUTS

Roundabouts can achieve accident reductions of between 50 90

percent when compared to stop-controlled or signalized intersections.Accident severity is also greatly reduced.

Conflicts at a Crossroads Conflicts at a Roundabout


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ROUNDABOUT FEATURESCentral Island: Raised area inthe center, around which

traffic circulates.Splitter Island: Raised orpainted area on an approach,used to separate entering andexiting traffic, deflect and

slow entering traffic, andprovide pedestrian refuge.

Circulatory Roadway: Curvedpath used by vehicles to travelaround the central island.

Apron: Mountable portion ofthe central island adjacent tothe circulatory roadway, toaccommodate the wheeltracking of large vehicles.

Yield line: Pavement marking usedto mark the point of entry fromthe approach into the circulatoryroadway. Entering vehicles mustyield to circulating traffic.


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ROUNDABOUT FEATURESAccessible PedestrianCrossings: Crossings set back

from the yield line to allowmovement of non-motorizedtravel. Splitter island is cut toallow pedestrians, wheelchairs,strollers and bicycles to passthrough.

Bicycle Treatments: Providebicyclists the option oftravelling through theroundabout either as a vehicleor as a pedestrian, depending

on the bicyclists level ofcomfort.Landscaping Buffer: Provided to

separate vehicular and pedestriantraffic, and to encourage pedestriansto cross only at designated crossinglocations. Also to improve aesthetics.


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Additional Design Elements at Roundabouts

SPEED REDUCTION

Good roundabout design requires enteringvehicles to negotiate a small enough radiusto slow speeds to no greater than 50km/h.

Once within the circulatory roadway,

vehicle paths are further deflected bythe central island, thus reducing speed.

DESIGN VEHICLE

Good roundabout design makes

accommodation for the appropriate designvehicle.

For small roundabouts, this may require anapron.


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ENTRY FLARES

Flare on an entry to a roundabout is thewidening of an approach to multiple lanesto provide additional capacity and storagebeyond the yield line.

SPLITTER ISLAND

All roundabouts (except mini roundabouts)have raised splitter island.

Mini roundabouts may have splitter islandsdefined only by pavement marking.

PEDESTRIAN CROSSING LOCATIONS

Pedestrian crossing are located at least onevehicle length upstream of the yield point.


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Roundabout Categories

Mini Roundabout


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Urban Compact Roundabout


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Urban Single Lane Roundabout


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Urban Double Lane Roundabout


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Rural Single Lane Roundabout


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TRAFFIC CONTROL SIGNAL

OBJECTIVES

OF TRAFFICCONTROLSIGNALS

To maintain orderly and smooth flow of vehicles

To reduce vehicle conflicts

To reduce delays

To reduce accidents

To reduce limited space entirely

To allow pedestrians to cross safely

To reduce use of traffic police

Traffic control signal is primarily used for control of vehicular andpedestrian movements, especially at intersections.

It is a device that directs traffic to stop and permits traffic toproceed.

Red: Vehicles must stop

Amber: Vehicles must slow down and prepare to stop

Green: Vehicles can proceed


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S has to be corrected for effects of gradient, turning radius andthe proportion of turning vehicles.


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Adjusted S = S x fg x ft x fl x fr


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(2) DETERMINATION OF Y

y = q / S

where q = actual flow on a traffic-signal approach in pcu/hrS = saturation flow for the approach in pcu/hr

The y value for a single phase is the highest y value from the

approaches in the phase.

For the whole junction, Y = yi

where yi = is the highest y value from the approaches within phase I

The Y value is a measure of occupancy of the intersection.

Preferably Y 0.85


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If Y > 0.85, it is suggested that the geometric design and thelayout of the intersection or the number of lanes be improved.

Conversion of veh/hr to pcu/hr is made using the table below:


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(3) DETERMINATION OF TOTAL LOST TIME PER CYCLE, L

L = (I a) + l

where I = Intergreen time = R + a

where R = all-red interval, a = amber time

a = amber time (usually 3 or 4 sec)

l = driver reaction time, or lost time, at the beginning of

green per phase

(usually set at 2 sec, but 0 7 sec can also be used)


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(5) DETERMINATION OF SIGNAL SETTINGS

Effective green time (g) is the green time plus the change interval

minus the lost time for a designated phase.

Total effective green time = Optimum cycle time Total lost time

g1 + g2 + g3 + + gn = Co L

Effective green time is given by the following formula:

gn = yn x (Co L)

Y

where gn = effective green time for the n-th phaseyn = calculated y-value for the same n-th phase


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Actual green time, G = g + l + R

Controller setting time, K = G a R

K = g l - a


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Chapter 3

Traffic Safety

1. Traffic Safety Issues

2. Road Safety Interventions

3. Road Safety Audit

What you will be

learning from

this chapter


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300,000 person are killed annually inroad accidents worldwide

10 to 15 million person injured annuallyin road accident worldwide

Developing countries 20 200 deaths per10,000 motor vehicles

Developed countries 2 5 deaths per10,000 motor vehicles

Cost of accidents in developing countries is 1%- 2% of the Gross National Product

Source : World Bank

d d id ff


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Feeling ofsorrow and

grief to lovedones

Physical pain anddisfigurement

Congestion, traveltime delay on road

and inefficiency oflogistic services

Physicaldisabilities

Governments willhave to bear thecosts of accidents

Financialproblems

ROAD ACCIDENTS: HOW

THEY AFFECT US

How do Road Accidents affect

people?


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Factors Contributing to Road

Accidents


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The 3E Solution

Education

Enforcement

Engineering

Road Safety Programs, Strategies andIntervention


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Education

early childhood road training to initialdriver training.

attitude changing programs

road safety education in school

exercises in pedestrian and cyclist safety

driver training courses

safety programmes for the elderly

campaigns (anti-speeding, seatbelt,helmet, drink driving etc)


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Enforcement

Based on Road Transport Act 1987/1999.

Impose summons (drank drivers, non-

wearing seatbelt, helmet, speeding etc) enforcing speed traps

speed limits on all roads

introduce public service as penalty
http://localhost/var/www/apps/conversion/tmp/MSc/Prof%20Radin/Road%20Safety%20Audit/AKTA%20PENGANGKUTAN%20JALAN.htmhttp://localhost/var/www/apps/conversion/tmp/MSc/Prof%20Radin/Road%20Safety%20Audit/AKTA%20PENGANGKUTAN%20JALAN.htm


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Engineering

Technology changes to motorvehicles:

- automatic transmission

- visibility systems

- anti-break locking systems

- injury attenuation systems, etc.


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Engineering (contd)

Road and traffic developments:

- Access control

- improved geometric design

- improved lighting and carriageway delineation

- improve road signing

- separation of vulnerable road user

- identification and treatment for a blackspots


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Pre-Crash Crash Post-Crash

Human 1. Education

2. Campaign3. Enforcement

1. Compliance to

Safety Devices

1. Skill of

Paramedic andFirst Respondents

Vehicle 1. Type Approval2. Road Worthiness

3. Active SafetyDevices

1. Installation ofPassive SafetyDevices

1. Ease ofEvacuation

2. Better RescueTool

Environment 1. Road EngineeringPrograms

1. Safer RoadFurniture

1. RehabilitationCentre (trauma)

Ch 1

BFC 32302 Traff ic Eng ineering and Safety Lecturer: Dr. Basil David Daniel


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Chapter 1

Traffic Flow

TRAFFIC STUDIES

Traffic Volume

Spot Speed

TRAFFIC FLOW THEORY

Traffic Flow Parameters

Speed, Flow & Density Relationship

CAPACITY & LEVEL OF SERVICE

Multilane Highway Capacity Study

What you will be

learning from

this chapter



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TRAFFIC FLOW THEORY

1) SPEED (v)

Speed is ......defined as rate of motion, or distance per unit time

Space Mean Speed, vs

is the average travel speed

TRAFFIC FLOW PARAMETERS

n

i

i

s

t

nLv

1

n = number of travel times observed

L = length of the highway segment (km)ti = travel time of the i-th vehicle totraverse the section (hr)

tnL

vs



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TRAFFIC FLOW PARAMETERSTime Mean Speed, vt

is the arithmetic mean of the measured speeds of all

vehicles passing a fixed roadside point during a given intervalof time (the individual speeds are known as spot speeds)

n = number of vehicles observed

vi = spot speeds (km/hr)

L = average length travelled by the vehiclesn

v

v

n

i

i

t

1

Relationship between Space Mean Speed and Time Mean Speed

s

2

s

st vvv

t

2

t

ts

vvv or

s2 = variance of the space mean speedt2 = variance of the time mean speed =

n

)vv( 2ti

n

t

L

vt



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Example 1Three vehicles pass a kilometer post at 60, 75 and 54 km/hr,respectively. What is the time mean speed of the three vehicles?

Also, find the approximate space mean speed.

km/hr633

547560

tv

783

)6354()6375()6360( 2222

t

km/hr8.6163

7863 sv



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TRAFFIC FLOW THEORY2) VOLUME (V)

Volume is ......

the number of vehicles observed or predicted to pass a pointduring a given time interval.

3) RATE OF FLOW (q)

Rate of flow is ......the number of vehicles passing a point during a given timeinterval less than 1 hour, but expressed as an equivalenthourly rate.

Thus, a volume of 200 vehicles observed in a 10-minute periodimplies a rate of flow of 1200 veh/hr.

200 = 1200

(10/60)


N


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TRAFFIC FLOW THEORY4) DENSITY (k)

Density is ......

the number of vehicles occupyinga given length of lane orroadway, averaged over time.

Usually expressed in vehicles/km.

Density can be measured directlythrough aerial photography.

Density can also be calculated usingthe equation:

k = q/v

where q = rate of flowv = speed

500 m

What is the

density ofsouthboundtraffic on thishighway?

N

k = 14 veh / 0.5 km

= 28 veh/km



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TRAFFIC FLOW THEORY5) SPACING (s)

Spacing is ......

the distance (meters) between successive vehicles in a trafficstream, measured from front bumper to front bumper.

6) HEADWAY (h)

Headway is ......the corresponding time (seconds) between successive vehiclesas they pass a point of a roadway.

Spacing and Headway are related to q, v and k:

k = 1000/s

h = s/v

q = 3600/h

k (in veh/km), s (in meters)

h (in sec), v (in m/s)

q (in veh/hr), h (in sec)



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TRAFFIC FLOW THEORY7) LANE OCCUPANCY (LO)

Lane Occupancy is ......

the ratio of the time that vehicles are present at a detectionstation in a traffic lane compared to the time of sampling.

LO = Total time vehicle detector is occupied = to

Total observation time T

to = L + C where L = average length of vehicle

vs C = distance between loop detector


TRAFFIC FLOW THEORY


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Density can be estimated using the expression ......

k = LO x 1000

L + C

Lane occupancy may also be expressed by R, which is

R = Sum of lengths of vehicles = LiLength of roadway section D

Then, density can be estimated using the expression ......

k = R/L where L = average length of vehicles


TRAFFIC FLOW THEORY


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UNINTERRUPTED FLOW

Occurs on facilities that have no fixed elements (such as trafficsignals or stop signs) external to the traffic stream, that causeinterruptions to traffic flow.

Traffic flow conditions are thus the result of interactions amongvehicles in the traffic system and between vehicles and thegeometric characteristics of the roadway/guideway system.

The driver of the vehicle does not expect to be required to stop byfactors external to the traffic stream

CATEGORIES OF TRAFFIC FLOW

Uninterrupted Flow facilities:Expressways, Exclusive bus lanes, Rail Transit Lines


TRAFFIC FLOW THEORY


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INTERRUPTED FLOW

Occurs on facilities that have fixed elements causing periodicinterruptions to traffic flow.

Traffic is stopped or significally slowed down periodically

irrespective of how much traffic exists.

The driver expects to be required to stop as and when required byfixed elements that are part of the facility

CATEGORIES OF TRAFFIC FLOW

Interrupted Flow facilities:

Signalized streets, Unsignalized streets with stop signs, Arterials,Pedestrian walkways, Bicycle paths.

*Note:Uninterrupted/Interrupted Flow are terms that describe the facility, andnot the quality of flow!


Answer This


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What type of facilities are these?

Uninterrupted flow facility or Interrupted flow facility?

UNINTERRUPTED FLOW

FACILITY

INTERRUPTED FLOW

FACILITY


TRAFFIC FLOW THEORY


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UNINTERRUPTED TRAFFIC FLOW MODEL

D

C

B

A

Congestion Capacity

Normal flow

Forced flow

Speed (km/hr)

Flow (veh/hr)


TRAFFIC FLOW THEORY


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Imagine several vehicles, driven by rational drivers along a section offreeway.

As vehicles speed and spacing increases, the speeds approach the freespeed, and drivers adopt their own speed when uninfluenced by othervehicles in the traffic stream (point C).

The dashed curve represents the normal flow behaviour if all drivers

were to have the same free speed (point D).

It has been observed that drivers are uninfluenced by other vehicles inthe traffic lane at flows about half the capacity flow (point B).

Maximum traffic density occurs (point A) when traffic has virtuallycome to a complete stop.

In the forced flow region, each vehicle adopts its minimum spacing andclearance distance.


TRAFFIC FLOW THEORY


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SPEED, FLOW and DENSITY relationship

Speed, v Speed, v

Flow, qDensity, k

Flow, q

A

A/B

v = A Bk

A/2

A/BA/2BDensity, k

A2/4B


TRAFFIC FLOW THEORY


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Speed-Density relationship


TRAFFIC FLOW THEORY


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Flow-Density relationship


TRAFFIC FLOW THEORY


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Speed-Flow relationship


TRAFFIC FLOW THEORY


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Maximum flow (qmax) occurs at optimal speed (vm) and optimal density(km).

qmax = vm x km

= vf x kj2 2

= vf x kj4

BFC 32302 Traff ic Eng ineering and SafetyLecturer: Dr. Basil David Daniel

HIGHWAY CAPACITY & LEVEL OF SERVICE


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100

CAPACITY is ......

the maximum hourly rate at which persons or vehicles reasonably can be

expected to traverse a point or a uniform section of a lane or roadway

during a given time period under prevailing roadway, traffic and control

conditions

LEVEL OF SERVICE (LOS) is ......

a qualitative measure describing operational conditions within a traffic

stream and their perception by motorists and/or passengers


MULTILANE HIGHWAY CAPACITY STUDY


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101

6 levels of service:

LOS A Very Good

LOS B

LOS C

LOS D

LOS E

LOS F Very Poor

Parameters which determine the

LOS of a highway:

Flow

Speed




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102

A MULTILANE HIGHWAY ......

Has a posted speed limit of 60 to 90 km/h.

Has a total of 4 to 6 lanes.

Often is divided (has a median), can also be undivided.

Is situated in suburban communities, leading into cities.

Is also situated along high-volume rural corridors connecting two cities.

Has traffic signals spaced at 3 km or less.

Accommodates 15,000 40,000 vehicles per day.

May accommodate as high as 100,000 veh/day when access across the

median is restricted and when all major crossings are grade separated.




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103

Divided highway

median

Undivided highway

Grade separatedcrossing

TWRTLLane

At-grade crossing

Two-way Right Turn LaneNote: In USA, TWLT L(Left turn)




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104

Under BASE CONDITIONS, full speed and capacity can be achieved.

The base conditions for a multilane highway are ......

3.6 m minimum lane width.

3.6 m minimum total lateral clearance in the direction of travel.

Only passenger cars in the traffic stream.

No direct access points along the roadway.

Highway is divided.

Free flow speed (FFS) is greater than 100 km/h.




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105

Total Lateral Clearance = Median Lateral + Shoulder Lateral

Clearance Clearance

Median Roadway Shoulder

1.6 m 1.2 m

Total Lateral Clearance = 1.6 + 1.2 = 2.8 m

* If lateral clearance (shoulder or median) is greater than 1.8 m, the lateral clearance

is taken as 1.8 m.




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106

Calculate the total lateral clearance.

1.2 m

Total Lateral Clearance =

2.4 m

1.8 + 1.2 = 3.0 m




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107

Calculate the total lateral clearance.

0.8 m1.25 m

Total Lateral Clearance =

2.5 m

T

1.7 m

0.8 + 1.25 = 2.05 m

T




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108

Methodology (accroding to HCM 2000)

Input

Geometric data

FFS or BFFS

Volume

BFFS Adjustment

Lane width

Median type

Access point

Lateral Clearance

Compute FFS

FFS

BFFS

Volume Adjustment

Peak-hour Factor

Number of Lanes

Driver population

Heavy vehicles

Compute flow rate

DetermineLOS




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109

(a) Field Measurement

Average of all passenger car speeds measured in field under low volume

conditions can be directly used as the FFS if such measurements were

taken at or below 1400 pc/hr/lane

DETERMINATION OF FREE FLOW SPEED (FFS)

(b) Estimation

FFS = BFFS fW fLC fM fA

where BFFS = base free flow speed

fw = adjustment for lane width

fLC = adjustment for lateral clearance

fM = adjustment for median

fA = adjustment for access point density




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110

(b) Estimation

BFFS is assumed to be 3 km/h lower than the 85

th

percentile speed.Recent studies suggests that BFFS is approximately 11 km/h higher than

the speed limits of 65 km/h and 70 km/h, and it is 8 km/h higher for 80

km/h and 90 km/h speed limits.

The BFFS is then reduced by the adjustment factors for lane width, lateral

clearance, median type and access point density.The adjustment factors can be determined from the tables in HCM2000.




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111

vP = V

PHF x N x fHV x fp

where ;

V = hourly volume (veh/hr)

PHF = peak hour factor

N = number of lanes (per direction)

fHV = heavy vehicles adjustment factor

fp = driver population factor

DETERMINATION OF FLOW RATE (vP)

Peak Hour Factor

PHF = V where: V = peak hourly volume

4 x V15 V15 = highest 15-minute volume




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112

fHV = 1

1 + PT (ET 1) + PR (ER 1)

where PT = percentage of trucks and buses

ET = passenger car equivalent for trucks and buses

PR

= percentage of recreational vehicles

ER = passenger car equivalent for recreational vehicles

* Neglect PR and ER , because there are no RVs in Malaysia!

Heavy Vehicle Adjustment Factor

Recreational

vehicle (RV)




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113

When the traffic stream is made up of vehicles driven by regular drivers (commuters,

or drivers familiar with the highway), the driver population factor, fP is taken as 1.00Driver population factor may range between 0.85 and 1.00

Driver Population Factor

DETERMINATION OF LEVEL OF SERVICE

Look up the Speed-Flow curve.

Locate the vP value on the x-axis and draw a vertical line upwards.

Determine the average speed, S. (S=FFS if vP

1400 pc/hr/ln)

Calculate density, D = vP / S.

Determine the LOS on basis of density region in which the point is located.

LOS is determined using the FFS and vP values.


MULTILANE HIGHWAY CAPACITY STUDY Note: If vp < 1400,S = FFS


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114

(1) Determine the LOS of a multilane highway, given that FFS is 82.5 km/h and vP =

926 pc/hr/ln.

Quick Excercise

D = vp/S

= 926 / 82.5

= 11.2 pc/km/ln

LOS C

S = FFS




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115

(2) Determine the LOS of a multilane highway, given that FFS = 62 km/h,

S = 75 km/h and vP = 1,540 pc/hr/ln.

Quick Excercise

D = vp/S

= 1,540 / 75

= 20.53 pc/km/ln

LOS D


Chapter 2


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Chapter 2

Geometric Design

4.1 SIGHT DISTANCE

Stopping Sight Distance

Passing Sight Distance

Intersection Sight Distance

Sight Distance on Horizontal Curves

Sight Distance on Vertical Curves

4.2 HORIZONTAL ALIGNMENT

4.3 VERTICAL ALIGNMENT

What you will be

learning from this

chapter

116

BFC32302 Traff ic Engin eering and Safety Lecturer: Dr. Basil David Daniel

HORIZONTAL ALIGNMENT


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Horizontal alignment is an important feature

in road design which enhances smooth

driving, comfort and safety for motorists.

Inappropriate alignment may:

Cause accidents motorists are not able to

maneuver their vehicles properly, or are

not aware of the need to change speed

Reduce capacity motorists will travel at

low speeds, hence reducing capacity

117

Horizontal alignment is applied when direction change involving two straight roads (road

) i i d



118/148

tangents) is required.

Road tangent 1

Road tangent 2Horizontal Curve

118


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MINIMUM CURVE RADIUS2

R = curve radius (m)



120/148

)(127 maxmax

2

minfe

VR

V = speed (km/h)

e = superelevation (%)

f = side friction factor

Derivation of the formula:

120



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121

JKR proposes a maximum superelevation of 6% for urban roads and 10% or rural roads.



122/148

Design Speed

(km/h)

Minimum Radius (m)

e = 6% e = 10%

120 710 570

100 465 375

80 280 230

60 150 125

50 100 85

40 60 5030 35 30

20 15 15

The desired minimum curve radius

proposed by JKR for roads:

The desired minimum curve radius

proposed by LLM for highways:

Design Speed

(km/h)

140 120 100 80

Minimum Radius

(m)

1000 650 450 240

122

Example:



123/148

A roadway is being designed for a speed of 120 km/h. At one horizontal curve, it is

known that the superelevation value is 8% and the side friction factor is 0.09.

Determine the minimum radius of curve (measured to the traveled path) that will

provide safe vehicle operation.

mfe

VR 6705.666)09.008.0(127 120)(127

22

123

Example:



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A horizontal curve is designed with a 700-meter radius. The curve has a tangent of

130 m and the PI is at station 102 + 50. Determine the stationing of PT.

T = R tan /2

130 = 700 tan /2

/2 = 10.52= 21.04

L = R/180 = ( 21.04 )(700)/180 = 257.05 m

Given the tangent is 130 m,

Stationing PC = (102 + 50) (1 + 30) = 101 + 20

Horizontal curve stationing is measured along the curve,

Stationing PT = (101 + 20) + (2 + 57.05) = 103 + 77.05

PC

PT

PI (102 + 50)

R = 700 m

L

T = 130 m

124

SUPERELEVATION TRANSITION



125/148

Tangent runout is the length of highway needed to change the normal cross section to the cross

section with the adverse crown removed.

Superelevation runoffis the length of highway needed to change the adverse crown removed to

the cross section with full superelevation.

2.5% 2.5% 2.5%

0%

2.5%

0%

e%

e%

125

ATTAINMENT OF SUPERELEVATION



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Transition from tangent to superelevation

Must be done gradually without appreciable reduction in speed or safety, andwith comfort

Change in pavement slopes must be consistent over a distance

Methods:

The length over which superelevation is developed should be adequate to provide

safe and comfortable riding quality and give good appearance

Criteria used to determine minimum lengths:

Rotate pavement about centerlineRotate about inner edge of the pavement

Rotate about outer edge of the pavement

Rate of rotation of the pavement

Relative grade of the pavement edges with respect to longitudinal grade

126

ROTATION OF PAVEMENT



127/148

127

Tangent

Runout

Superelevation RunoffNormal

Crown

Full Superelevation Normal

Crown

Tangent

Runout

Superelevation Runoff



128/148

Outer edge

Inner edge

Outer edge

Inner edge

0%

-2.5%

+2.5%

+e%

-e%

Road Cross section

Superelevation Diagram

Normal Crown Remove Crown

TS

SC CS

ST

+e%

-e%

+2.5%-2.5%-2.5%

-2.5%-2.5%0% +e%

-e%

+2.5%

-2.5%-2.5%

-2.5%-2.5%

0%

Adverse

Crown

Removed

128

SUPERELEVATION PROFILE

http://localhost/var/www/apps/conversion/tmp/Media/Superelevation.swfhttp://localhost/var/www/apps/conversion/tmp/Media/Superelevation.swf


129/148

Outside edge of

traveled way

Inside edge of

traveled way

129



130/148

130



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131



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132



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133

HORIZONTAL DESIGN EXAMPLEBFC32302 Traff ic Engin eering and Safety Lecturer: Dr. Basil David Daniel
http://localhost/var/www/apps/conversion/tmp/PDF%20Files/Example%20of%20Horizontal%20Curve%20Design.pdfhttp://localhost/var/www/apps/conversion/tmp/PDF%20Files/Example%20of%20Horizontal%20Curve%20Design.pdf


134/148

In the diagram given above, P0 is the point of intersection while points P1 and P2 are located on two

separate urban (U5) road tangents. A circular curve with allowance of transition curves will be needed to

connect the two roads. The proposed circular curve radius is 400 m and the design speed is 80 km/h.

The co-ordinates of P0 is (-30342.497, 32349.868), P1 is (-29940.497, 32301.369) and P2 is (-

30606.966, 32759.868). The chainage for P1 is 265.455 m. The length between point P1 and point P0 is

404.91499 m and the angle of deflection is 501738.

(a) Propose a suitable transition curve length and superelevation.

(b) Design the horizontal curve.

(c) Determine the chainage for points TS, SC, CS and ST.

(d) Check whether the gradient of superelevated pavement is satisfactory.

P0

P1

P2

404.91499 m

501738

134


VERTICAL ALIGNMENT


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Vertical alignment controls

how the road follows the

existing terrain.

Grades are connected with

parabolic vertical curvescalculated using the stopping

sight distance and grade

difference.


136/148


Critical Grade Length Design speed(km/h)

Grade (%) Critical Grade

Length (m)


137/148

The performance of a vehicle on a

grade is not only influenced by

maximum grade but also the

grade length.

The critical grade length is the

maximum length a loaded truck

can traverse a climbing lane

without significantly reducing its

speed.

Suggested critical grade

lengths (JKR)

(km/h) Length (m)

120 3

4

5

500

400

300

100 4

5

6

500

400

300

80 5

6

7

500

400

300

60 6

7

8

300

250

200

50 7

8

9

250

200

170

40 8

9

10

200

170

150


Design of climbing lane according to JKR specifications:


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Climbing lane starts atthe foot of the grade

with taper length not

less than 50 m.

Climbing lane width is 3.25 mor equal to the normal travel

lane width.

Adequate traffic

signs andpavement

markings must be

provided to ensure

drivers are aware

of the limitations

of movements.

Shoulder width must not beless than 1.25 m. Desirably,

shoulder length must be

equal to the normal lane

width.

Climbing lane must

end at least 60 m

beyond the crest ofthe curve, or when

safe passing sight

distance is

achieved. The

desired end taper

length is 100 m.


Vertical Curve Length

Th i i ti l l th i i b th f l L kA h A i th


139/148

The minimum vertical curve length is given by the formula L = kA, where A is the

algebraic difference between the grades and k is the horizontal distance required to

influence a 1% change in gradient.

k is also the measure of curvature for vertical curves.

Suggested minimum k values for vertical curves (JKR)

Design speed km/h Minimum k value

Sag Curve Crest curve

120 60 120

100 40 60

80 28 30

60 15 15

50 12 10

40 10 10

30 8 5

20 8 5


VERTICAL CURVES


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Vertical curves are employed to provide gradual change between roadway grades.

Vertical curves should be simple in application and should result in a design that is safe

and comfortable in operation, pleasing in appearance, and adequate for drainage.

Types of curves:

Crest Curves Sag Curves


Elements of a Vertical CurveVIP


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BVC

V

EVC

A% = G1 G2

G1 G2E

y

Y

x

L

L/2

2xL200

Ay y

100

xGY 1


Elements of a Vertical Curve


142/148

VIP = vertical intersection point

BVC = beginning of vertical curveEVC = end of vertical curve

L = vertical curve length

A = algebraic difference between grades G2 and G1x = horizontal distance from a point on the curve, measured from BVC

y = offset

E = elevation of minimum/maximum point on the curve, measured from BVCG1 and G2 = tangent grades


Maximum/minimum point on the curve:


143/148

2211

21

1

xL200

)GG(x

100

GY

xL200

Ax

100

GY

yx

100

GY

xL100

)GG(

100

G

dx

dY 211

0dx

dY At maximum/minimumpoint,

ALGx 1maxmin/

Therefore,

maxmin/maxmin/ YBVC@elevationy

where,

2maxmin/

maxmin/1maxmin/ )x(L200

A

100

xGY


Elevation of a point on the curve:


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LPn

yn

Lx

xn

2

L

xe4

800

AL

nnnx yLPL

LPn = G1*(Interval) + LPn-1

yn =

where e =


145/148


Solution:

A = 2 (-3) = 5


146/148

A 2 ( 3) 5

e = AL/800 = 5(300)/800 = 1.875

G1 x Interval = 0.02 x 25 = 0.50 m

x LP x/L (x/L)2 yn = 4e(x/L)2 Lx = LP - yn Remarks

0 18.00 0.0000 0.0000 0.0000 18.000 BVC

25 18.50 0.0833 0.0069 0.0521 18.448

50 19.00 0.1667 0.0278 0.2083 18.792

75 19.50 0.2500 0.0625 0.4688 19.031

100 20.00 0.3333 0.1111 0.8333 19.167

125 20.50 0.4167 0.1736 1.3021 19.198

150 21.00 0.5000 0.2500 1.8750 19.125

175 21.50 0.5833 0.3403 2.5521 18.948

200 22.00 0.6667 0.4444 3.3333 18.667

225 22.50 0.7500 0.5625 4.2188 18.281

250 23.00 0.8333 0.6944 5.2083 17.792

275 23.50 0.9167 0.8403 6.3021 17.198

300 24.00 1.0000 1.0000 7.5000 16.500 EVC


Determination of the maximum point on the curve:

120300*2LG1


147/148

m1205

3002

A

LGx 1max

2maxmin/

maxmin/1max )x(L200

A

100

xGy m2.1)120(300*200

5

100

)120(2 2

ymax = elevation@BVC + Ymax = 18.00 + 1.2 = 19.2 m


Sketching of the vertical curve:


148/148

18.0

00

18.4

48

18.7

92

19.0

31

19

.167

19

.125

18.9

4

8

18.6

67

18.2

81

17.7

92

17.1

98

16.5

00

19

.200

19

.198

bfc 32302 revision final

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