Traffic Impact Assessment (TIA) and Level of Service (LoS)

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CDr.ZaraBizan
Developer
Architect/
Town Planner
Local Authority
Appointment of a
Transport Engineer
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Discussion to determine
the scope, study area
and study methodology
Collate existing data
and information
Traffic Study
Analyses:
- Trip generation
- Model split
- Trip distribution
- Trip assignment
- Analyses of LOS
- Problem evaluation
- Proposal to alleviate or
reduce the identified problem
Review the original
lay-out plan and
propose any improvement
to the client and land use
FINAL
REPORT
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TRAFFIC IMPACT ASSESSMENT (TIA)
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Process flow

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Existing Situation
Analyses
Impact to the
Road Network
Road Safety
Internal Lay-out
Parking Space
Public Transport
Pedestrian,
Bicycle and
Disable Facilities
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CONTENT OF
TIA REPORT
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All development
will generate traffic
into current or future
transport facilities
All big development
will generate internal
traffic
Implication
Development

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To obtain degree of control
at access requested by the
private/goverment entities
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To determine what type
of access required to be
considered and constructed
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To offer alternatives
solution to traffic
improvement as
well as measures
for the road users
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To predetermine
future expansion
if its required
TIA is an important tool used to determine the transportation
and traffic impact of a proposed site development project
(upon full development) on the surrounding traffic and
transportation systems.
It identifies the need for mitigation measures for a
transportation system to reduce congestion, as well as to
maintain or improve road safety.
Local Authorities will use TIA as basis for assessing and
apportioning a developer’s contribution to road improvements.
Local Authorities also will use TIA to evaluate Traffic
Management Plan proposals.
Provides necessary technical input to other relevant reports
such as Environmental Impact Assessment, Social Impact
Assessment, Development Plan (Structure and Local Plan),
Transport Master Plan and the Road Safety Audits.
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WhatisTIA?
WHYDOWENEEDTIA?
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Traffic Impact
AssessmentTIA
When impacts are not accurately projected
through the traffic analysis process, the best
decisions may not be made. Poor decisions
can result in traffic congestion, safety issues,
or unnecessary improvements.
THE IMPORTANCE OF TIA?
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A
B
C
D
E
70
60
50
40
30
No congestion
Free flow with low traffic
volumes and high speeds
No congestion
Reasonably free flow, but
speed depends on traffic flow
Moderate congestion
Unstable flow ; Restricted drivers
chosen speed
Severe congestion
Very unstable flow possible
short stoppages
NO DELAYS
NO DELAYS
MINIMAL DELAYS
MINIMAL DELAYS
SIGNIFICANT DELAYS
CONSIDERABLE DELAYS
AVERAGE TRAVEL
SPEED (KM/H)
TECHNICAL DESCRIPTION
F30
Extreme congestion
Unacceptable congestion
stop-and-go traffic ; forced flow
LOS
LOS provides
an indication
or measure of
the operational
condition of
the facility
concerned.
A range from
“A” to “F” is
applicable; LOS
“A” represents
an excellent
level of
operational
condition,
while LOS “F”
an undesirable,
exceedingly
congested and
failed situation.
Level
of
Service
Reference: Road Traffic Volume Malaysia (RVTM) 2018
Minimal congestion
Stable flow zone, but with driver less
able to travel at their own chosen speed

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Delaypervehicle(seconds)< 10
Highestqualityofservice.Freetraffic
flowwithfewrestrictionon
maneuverabilityorspeed
VeryShortDelay
A
Delaypervehicle(seconds)10-15
Stabletrafficflow.Speedbecoming
slightlyrestricted.Lowrestricted
onmaneuverability
NoDelays
D
Delaypervehicle(seconds)25-35
Trafficflowbecomingunstable.
Speedssubjecttosuddenchange.
Passingisdifficult.
MinimalDelays
B
Delaypervehicle(seconds)35-50
Unstabletrafficflow.
Speedschangequicklyand
maneuverabilityislow
SignificantDelays
E
Delaypervehicle(seconds)15-25
Stabletrafficflow,butless
freedomtoselectspeed,
changelanesorpass
MinimalDelays
C
Delaypervehicle(seconds)> 50
Heavilycongestedtraffic.
Demandexceedscapacity
andspeedsvarygreatly.
ConsiderableDelays
F
LevelofService(LOS)
LevelofService(LOS)
LevelofService(LOS)
LevelofService(LOS)
LEVEL OF SERVICE (LOS) for Unsignalized Intersections
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6. A < 10Delay per vehicle
(seconds)
L
evelofServic
e
B 11-20Delay per vehicle
(seconds)
L
evelofServic
e
C 21-35Delay per vehicle
(seconds)
L
evelofServic
e
D 36-55Delay per vehicle
(seconds)
L
evelofServic
e
E 56-80Delay per vehicle
(seconds)
L
evelofServic
e
F >80Delay per vehicle
(seconds)
L
evelofServic
e
TrafficSignalConditions
GeometricConditions
SignalCoordinatin
CycleLength
Protectedleftturn
Timing
Etc.
Pre-timedortraffic
activatedsignal
SignalCoordinatin
CycleLength
Protectedleftturn
TrafficCondition
Percentoftrucktraffic
Numberofpedestrians
Etc.
FACTORAFFECTINGLOSOFSIGNALIZEDINTERSECTIONS
LEVELS OF SERVICE (LOS)
forIntersectionswith
TrafficSignals
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Source: 2000 HCM, Exhibit 16-2, Level of Service Criteria for Signalized Intersec�ons