Capacity and Level of Service at Signalized

8/9/2019 Capacity and Level of Service at Signalized

1/20

capacity and level of service

at signalized intersection• The level of service at any intersection on highway has a significant effect on theoverall operating performance of that highway. Thus improvement of the level ofservice oat each intersection usually results in an improvement of the overall

Operating performance of the highway.

Analysis procedure that provides for the determination of capacity or

lever are:

a. Flow b. Distribution of traffic

c. Geometric characteristics

d. And ignalization system


2/20

!".! D#F$%$T$O% OF O 'O&&O% T#(&

• Permitted turning movements is made within gaps of opposing traffic stream

or through a conflicting pedestrian flow.

• Protected turns are those protected from any conflicts with vehicles in an

opposing stream or pedestrians on a conflicting crosswal).

• Yellow change and red clearance interval is the sum of the intervals *given

in seconds+ that are provided between phases to allow vehicular and pedestrian

traffic to clear the intersection before conflicting movement are released.

• Geometric conditions is a term used to describe the roadway characteristic of

the approach.

• Signalization conditions is the term used to describe the signal operation.

• Flow rate v/s pro,ected demand *v+ on a approach or lane group to the

saturation flow rate *s+

• Lane group consists of one or more lanes that have a common stop line- carry

a set of traffic streams- and whose capacity is shared by all vehicles in the

group.


3/20

• An analysis period (T is the time intervals selected

to evaluate am intersection by applying the procedure

once.

• The study period is the time period for which the

results of the analysis are applicable and may consist

of one or more consecutive analysis periods.• !est in "al# mode enable for a phase- this mode will

dwell in wal) ecept when there are conflicting calls

• Pedestrian clear interval (P$% sometime )nown as

the pedestrian change interval allow pedestrian who

leaves the curb during the wal) interval to arrive at the

opposite curb or median.


4/20

$APA$&TY AT S&G'AL&)* &'T)!S)$T&+'

• &aimum rate of flow to sub,ect lane group that can

go through the intersection under prevailing traffic-

roadway- signalized conditions

• Overall capacity of the intersection is not considered.• #mphasised on suitable facilities movement of the

intersection.

•

/evel of service and capacity should be analysedseparately


5/20

SAT,!AT&+' FL+" +! SAT,!AT&+' FL+"

!AT)

• The concept of saturation flow or saturation flow

rate*s+ is used to determine capacity of a lane group.

• &aimum flow rate on the approach or lane groupthat can go through the intersection under prevailing

traffic and roadway conditions when !""0 effective

green time is available.


6/20


7/20

The critical v/c ratio -or the whole intersection


8/20

A'ALYS&S L).)LS A'* P)!F+!A'$) )AS,!)S F+! L).)L +F

S)!.&$) AT S&G'AL&)* &'T)!S)$T&+'S

There are three *1+ analysis levels for determining the level of

services */O+

• Operational

• Design and

• 2lanning and preliminary engineering

!. Operational level uses detailed information on:

•.

Traffic•.Geometric

•.ignalization characteristics for a comprehensive analysis of the

intersections.


9/20

3. Design analysis level is used when an intersection is being designed for a given

/O.

(e4uires:

5 Traffic 5Geometric

5ignalization characteristics

5Desired /O.

1. 2lanning and preliminary engineering analysis level uses

. basic and default values to evaluate a given intersection

. or planned overall eisting performance of a signalized intersection

. (e4uires least amount of site5 specific data.

&odes used for evaluating performance measures for 4uality operation at the

intersection:

. Automobiles

. 2edestrian

. 6icycle


10/20

The per-ormance measures include0

• Demand volume-to- capacity ratio v/c

• Queue storage ratio

• Automobile delay

• Pedestrian circulation area

• Pedestrian perception score• Pedestrian delay for walking

• Bicycle delay

• Bicycle perception score for bicycles

The !" is considered as a performance measure and it iscomputed separately for each of the modes considered#

The in$uence area in analysis should be at least %&'ftbackward from the stop line of each leg of the intersection#


11/20

1234 L).)L +F S)!.&$) $!&T)!&A AT S&G'AL&)*

&'T)!S)$T&+'S

/O 'riteria for the Automobile &ode

These procedures deal with the computation of the level of

service at each lane group- intersection approach- and at the

intersection as whole.

TA6/# !".!


12/20

L+S $riteria -or 'onautomotive (Pedestrian and

5icycle ode

The criteria for the nonautomotive modes are based on:

• cores computed from factors described as either performance

measures sure as:

•

2edestrian delay• $ndicators of the intersection characteristics

• 2edestrian corner circulation area

Table !".3 gives the relationship between the scores and the /O

for the nonautomotive mode.


13/20

automo7ile can 7e categorized into -our (8 group

• Traffic characteristics

• Geometric design• ignal control

• Other

Traffic characteristics

The demand flow rate5vehicles that arrive at the intersection divided bythe analysis period.

The right5turn5on5red *(TO(+ flow rate is the 4uotient of the number of

vehicles that turn right during analysis period and is epressed in terms of

an hourly flow.

2latoon ratio5how well a movement group progresses through theintersection and depends on the percentage of vehicles that arrive during

the green indication


14/20

• TAB( )'#* A+D TAB( )'#&


15/20

The upstream -iltering ad9ustment -actor (&

,)#'-'#.)0%#123'#'.

• &nitial 6ueue is the number of vehicles that are at the intersection at

the start of the analysis period of the movement group under

consideration.• 6ase saturation flow rate*+ is the maimum rate of flow across the

stop line. $t is associated with the following conditions:o Traffice lanes at least !3 ft wide

o %o heavy vehicles in the traffic stream

o A flat gradeo %o par)ing

o %o buses that stop at the intersection

o #ven lane utilization

o %o turning vehicles


16/20

The lane utilization ad,ustment factor *Flu+ is used

to ad,ust the ideal saturation flow rate The pedestrian flow rate 5

number of pedestrians in cross wal) that interrupt the flow of

right5turning vehicles during analysis period.

• The bicycle flow rate 7number of bicycles with a travel path

that results in an interruption of the flow of right 7 turning

vehicles from the approach under consideration during the

analysis period.

• The on5street par)ing maneuver rate 7 number of par)ing

maneuvers per during the analysis period that have an impact

on the intersection leg.

• The local bus stopping rate5the number of buses per hourduring analysis period that bloc) traffic by stopping

embar)ing or disembar)ing passengers within 38"ft.


17/20

Geometric *esign

Geometric elements of the intersection that have some

impact or the flow of traffic.

%umber of lanes

Average lane width %umber of receiving lanes

Turn bay length

2resent of on5street par)ingApproach grade


18/20

Signal control

elements provide input data for the signal control data are:

a. 2re5timed

b. semi5actuated

c. Fully actuated

d. And coordinated5actuated mode.

+ther

• The area type describe the activities in the are at which the

intersection is located.

• 9ave significant effect on:

peed

aturated volume at an approach.


19/20

COMPUTATION OF

PEDESTRIANS ANDBICYCLES FACTOR


20/20

STEPS"T(P )

4!5P6T( P(D("T7,A+ !446PA+48 A9T(7 Q6(6( 4(A7"

"T(P %

D(T(75,+( 7((:A+T 4!+9,4T ;!+( !446PA+48

"T(P <

D(T(75,+( 6+!446P,(D T,5(

"T(P *

D(T(75,+( "AT67AT,!+ 9!= 7AT( AD>6"T5(+T 9A4T!7

Capacity and Level of Service at Signalized

Documents

Transcript of Capacity and Level of Service at Signalized