Tteng 441 traffic engineering fall 2021 part5

Fall 2021/ ElDessouki . TTENG 441 Traffic Engineering 271

Intersection Control:
Conflict Points for At-Grade Intersection
 Crossing: 16
 Merging: 8
 Diverging: 8
273
. TTENG 441 Traffic Engineering
Fall 2021/ ElDessouki

Intersection Control:
Hierarchy of Control at Intersections:
 Level 1:
Basic Rules of Driving:
 Right Hand traffic has the ROW
 Through movement has the ROW over turning movements
If unsafe then:
 Level 2:
Direct Assignment for ROW: STOP or Yield Sign
If capacity insufficient then:
 Level 3:
Proportional Shared Assignment for ROW: Traffic Signal
274

Intersection Control: Level 1
Sight Distance Triangle: Safety Check
 Steps of Analysis:
1- Assume:
2- Determine the actual location of
Vehicle B:
3- Determine the stopping distance for
vehicle B.
4- For the intersection to be safely operated
under basic rules of the road.
Stopping
A
A d
d 
 
b
d
d
a
d
A
A
actual
B


*
Stopping
B
min
B d
d 
min
B
actual
B d
d 
275

70
km/hr 70
km/hr
5 m
18 m 6
m
16 m
50
km/hr
 Example 1:
Evaluate the safety of the shown intersection to operate under basic rules of the
road.
276

 Example 2:
The shown intersection is located in proposed residential subdivision plans, where the expected
traffic speed is 25 km/hrs. In order to approve the plans you have to do the following:
a) Evaluate the safety of this intersection to operate under basic rules of the road (Level 1)
b) Make the optimum adjustments to construction boundaries ( ‫اﻟﺒﻨﺎء‬ ‫)ﺣﺪود‬ such that these
intersections will operate safely under Level 1 traffic control
277

Stop Sign Sight Distance Triangle: Safety Check
The distance to the collision point ( dA) has three components:
 Distance from the driver’s eye to the front of the vehicle (assumed to be 2.4 m )
 Distance from the front of the vehicle to the curb line (assumed to be 3.0 m)
 Distance from the curb line to the center of the right-most travel lane approaching
from the left, or from the curb line to the left-most travel lane approaching from
the right
Then,
dA-STOP = 5.40 + dcl
Where,
dA-STOP = Distance of Vehicle A on STOP- controlled approach from the collision
point (meters)
dcl = Distance of curb line to the center of the closest travel lane from the direction
under consideration (meters)
278

Stop Sign Sight Distance Triangle: Safety Check (cont.)
 The required sight distances for Vehicle B, on the major street for STOP-
controlled intersections is found as follows:
Then,
dB-min = Smaj * tg
Where,
dB-min = Distance of Vehicle A on STOP- controlled approach from the collision
point (meters)
Smaj = Design speed on major approach in (m/sec.)
tg = Average gap accepted by minor street driver to enter the major road (sec.)
279

Stop Sign Sight Distance Triangle: Safety Check (cont.)
 Example:
Time gap= 7.5 sec.
Speed = 65 km/hr
280

STOP and Yield Sign
STOP control Warrants (MUTCD 2009) :
Guidance: At intersections where a full stop is not necessary at all times,
consideration should first be given to using less restrictive measures such as
YIELD signs
The use of STOP signs on the minor-street approaches should be considered if
engineering judgment indicates that a stop is always required because of one or
more of the following conditions:
I. The vehicular traffic volumes on the through street or highway exceed 6,000 vehicles
per day;
II. A restricted view exists that requires road users to stop in order to adequately observe
conflicting traffic on the through street or highway; and/or
III. Crash records indicate that three or more crashes that are susceptible to correction by
the installation of a STOP sign have been reported within a 12-month period, or that
five or more such crashes have been reported within a 2-year period. Such crashes
include right-angle collisions involving road users on the minor-street approach
failing to yield the right-of-way to traffic on the through street or highway.
281

STOP and Yield Sign
Yield Sign Warrants (MUTCD 2009) :
YIELD signs may be installed:
I. On the approaches to a through street or highway where conditions are such that a full
stop is not always required.
II. At the second crossroad of a divided highway, where the median width at the
intersection is 30 feet or greater. In this case, a STOP or YIELD sign may be installed
at the entrance to the first roadway of a divided highway, and a YIELD sign may be
installed at the entrance to the second roadway.
III. For a channelized turn lane that is separated from the adjacent travel lanes by an island,
even if the adjacent lanes at the intersection are controlled by a highway traffic control
signal or by a STOP sign.
IV. At an intersection where a special problem exists and where engineering judgment
indicates the problem to be susceptible to correction by the use of the YIELD sign.
V. Facing the entering roadway for a merge-type movement if engineering judgment
indicates that control is needed because acceleration geometry and/or sight distance is
not adequate for merging traffic operation.
282

STOP and Yield Sign
Warrants for Multiway STOP Control (MUTCD 2000, 2009) :
The following criteria should be considered in the engineering study for a multiway STOP sign:
A) Where traffic control signals are justified, the multiway STOP is an interim measure that can be
installed quickly to control traffic while arrangements are being made for the installation of the traffic
control signal.
B) A crash problem, as indicated by five or more reported crashes in a 12-month period that are
susceptible to correction by a multiway STOP installation. Such crashes include right- and left-turn
collisions as well as right-angle collisions.
C) Minimum volumes:
1) The vehicular volume entering the intersection from the major street approaches (total of both
approaches) averages at least 300 veh/h for any eight. hours of an average day.
2) The combined vehicular, pedestrian, and bicycle volume entering the intersection from the minor
street approaches (total of both approaches) averages at least 200 units/h for the same eight
hours, with an average delay to minor-street vehicular traffic of at least 30 s/veh during the highest
hour.
3) If the 85th percentile approach speed of the major highway exceeds 70km/hr, the minimum
vehicular volume warrants are 70% of the above values.
D) Where no single criterion is satisfied, but where criteria B, C1, and C2 are all satisfied to 80% of the
minimum values. Criterion C3 is excluded from this condition.
283

STOP Sign Capacity Analysis (HCM 2000 Ch 17)
284

285

286

287

Critical Gap Estimation:
288

Base Critical Gap :
Follow-up Time:
289

Potential Capacity(HCM method):
290

291

292

Traffic Signalization
When, Level 2 is not sufficient to control the intersection safely,
then we move to a signalized control, But we must take into
consideration the following:
 The cost involved in installation of traffic signals (e.g., power
supply, signal controller, detectors, signal heads, and support
structures, and other items) is considerably higher than for
STOP or YIELD signs and can run into the hundreds of
thousands of dollars for complex intersections.
 Because of this, and because traffic signals introduce a fixed
source of delay into the system, it is important that they not be
overused; they should be installed only where no other
solution or form of control would be effective in assuring
safety and efficiency at the intersection.
293

Traffic Signalization
MUTCD Warrants for Signalized Intersection:
Warrant 1, Eight-Hour Vehicular Volume
Warrant 2, Four-Hour Vehicular Volume
Warrant 3, Peak Hour
Warrant 4, Pedestrian Volume
Warrant 5, School Crossing
Warrant 6, Coordinated Signal System
Warrant 7, Crash Experience
Warrant 8, Roadway Network
Warrant 9, Intersection Near a Grade Crossing
294

‫ﺮﳼ‬
‫ﯾﺔ‬‫ر‬‫اﳌﺮو‬ ‫ﻠﺴﻼﻣﺔ‬ ‫اﻟﺴﻌﻮدﯾﺔ‬ ‫اﻣﻜﻮ‬‫ر‬ٔ
Aramco Chair for Traffic Safety Research 295

Design and Analysis of Traffic Signals: Basics Terms
Components of Traffic Signal:
Cycle. A signal cycle is one complete rotation through all of the
indications provided. in general, every legal vehicular
movement receives a “green” indication during each cycle,
although there are some exceptions to this rule.
Cycle length. The cycle length is the time (in seconds) that it
takes to complete one full cycle of indications. It is given the
symbol “ C ”
Phase. A signal phase consists of a green interval, plus the
change and clearance intervals that follow it. It is a set of
intervals that allows a designated movement or set of
movements to flow and to be safely halted before release of a
conflicting set of movements.
297

Components of Traffic Signal ( cont.):
Interval. The interval is a period of time during which no signal indication changes. It is the smallest unit of time described
within a signal cycle. There are several types of intervals within a signal cycle:
 Change interval. The change interval is the “yellow” indication for a given movement. It is part of the
transition from “green” to “red “ in which movements about to lose “green” are given a “yellow” signal, while
all other movements have a “red” signal. it is timed to allow a vehicle that cannot safely stop when the “green”
is withdrawn to enter the intersection legally. The change interval is given the symbol “Yi” for movement(s) i.
 Clearance interval. The clearance interval is also part of the transition from “green” to “red” for a given set of
movements. During the clearance interval, all movements have a “red” signal. it is timed to allow a vehicle that
legally enters the intersection on “yellow” to safely cross the intersection before conflicting flows are released.
The clearance interval is given the symbol “ARi” (for “all red”) for movement(s) i.
 Green interval. Each movement has one green interval during the signal cycle. During a green interval, the
movements permitted have a “green” light, while all other movements have a “red” light. The green interval is
given the symbol “Gi”or movement(s) i.
 Red interval. Each movement has a red interval during the signal cycle. All movements not permitted have a
“red” light, while those permitted to move have a “green” light. In general, the red interval overlaps the green
intervals for all other movements in the intersection. The red interval is given the symbol “Ri” for movement(s)
i.
298

Types of Signal Operation:
Pre-timed operation. In pre-timed operation, the cycle length, phase sequence,
and timing of each interval are constant. Each cycle of the signal follows
the same predetermined plan.
“Multi-dial” controllers will allow different pre-timed settings to be
established. An internal clock is used to activate the appropriate timing. in
such cases, it is typical to have at least an AM peak, a PM peak, and an off-
peak signal timing.
299

Semi-actuated operation. in semi-actuated operation, detectors are placed on
the minor approach(es) to the intersection; there are no detectors on the
major street. The light is green for the major street at all times except when
a “call” or actuation is noted on one of the minor approaches. Then, subject
to limitations such as a minimum major-street green, the green is
transferred to the minor street. The green returns to the major street when
the maximum minor street green is reached or when the detector senses that
there is no further demand on the minor street.
300

Fully-actuated operation. Full actuated operation. In full actuated operation,
every lane of every approach must be monitored by a detector. Green time
is allocated in accordance with information from detectors and
programmed “rules” established in the controller for capturing and
retaining the green. In full actuated operation, the cycle length, sequence of
phases, and green time split may vary from cycle to cycle.
301

Adaptive Traffic Control.
• Automatically adapt to unexpected changes in traffic conditions.
• Improve travel time reliability.
• Reduce congestion and fuel consumption.
• Prolong the effectiveness of traffic signal timing.
• Reduce the complaints that agencies receive in response to outdated signal
timing.
• Make traffic signal operations proactive by monitoring and responding to gaps in
performance.
Alternative:
Adaptive Control Software Lite (ACSLite) is a specific adaptive signal control
technology developed by the FHWA through a public-private partnership.
ACSLite takes advantage of typical signal system architecture and works with
existing control, detection, and communications configurations to cost-
effectively deliver adaptive control that is easy-to-deploy and produces
comparable performance to traditional adaptive systems.
302

Left Turn Treatment :
 The modeling of signalized intersection operation would be
straightforward if left turns did not exist. (McShain & Ross)
There are three methods for modeling Left Turn Movements:
1. Permitted left turns. A “permitted” left turn movement is one that is made
across an opposing flow of vehicles. The driver is permitted to cross
through the opposing flow, but must select an appropriate gap in the
opposing traffic stream through which to turn.
2. Protected left turns. A “protected” left turn movement is made without an
opposing vehicular flow. The signal plan protects left-turning vehicles by
stopping the opposing through movement. This requires that the left turns
and the opposing through flow be accommodated in separate signal phases
and leads to multiphase (more than two) signalization.
3. Compound left turns. More complicated signal timing can be designed in
which left turns are protected for a portion of the signal cycle and are
permitted in another portion of the cycle.
303

Design and Analysis of Traffic Signals: Discharge Headways,
Saturation Flow, Lost Times, and Capacity
Discharge Headways:
During RED time interval, a queue builds up, then when the signal turn into
Green interval, the queue start discharging. As the queue of vehicles
moves, headway measurements are taken as follows:
 The first headway is the time lapse between the initiation of the GREEN
signal and the time that the front wheels of the first vehicle cross the stop
line.
 The second headway is the time lapse between the time that the first
vehicle’s front wheels cross the stop line and the time that the second
vehicle’s front wheels cross the stop line.
 Subsequent headways are similarly measured. Only headways through the
last vehicle in queue (at the initiation of the GREEN light) are considered
to be operating under “saturated” conditions.
304

Discharge Headways (cont.):
305
Vehicles discharging at
state of Saturation

Discharge Headways (cont.):
306
h1 h2 hi
h4 hn
h3

 Saturation Discharge Headway (h):
After the 4th or 5th vehicle , the average headways will tend towards a
constant value which is referred to as the saturation headway (h)
307
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Headway
(sec)
Vehicle #
h

 The base saturation flow rate (S) is defined as the discharge rate
from a standing queue in a 3.6-m-wide lane that carries only through
passenger cars and is otherwise unaffected by conditions such as
grade, parking, and turning vehicles.
Calculating the Saturation Flow Rate: During the saturation flow state,
if the average vehicle is consuming a time headway (h) to pass, then
the hourly flow rate at saturation (s) can be calculated as following:
308
le)
(sec/vehic
headway
discharge
n
stauratio
Average
-
h
our/lane)
(vehicle/h
Rate
Flow
n
Saturatio
-
S
where
h
S
,
3600


 Start-Up lost time (l1) :
Is defined as the time lost at the beginning of the Green interval by the
first few vehicles in the queue. (typically the first 4 vehicles)
309
 




4
1
i
i
1 h
h
l
0.00
0.50
1.00
1.50
2.00
2.50
3.00
3.50
4.00
1 2 3 4 5 6 7 8 9 10 11 12 13 14
Headway
(sec)
Vehicle #
h
Start-Up lost time (l1)

 Clearance lost time (l2) :
 There is also a lost time associated with stopping the queue at
the end of the GREEN signal. This time is more difficult to
observe in the field, as it requires that the standing queue of
vehicles be large enough to consume all of the GREEN time
provided. In such a situation, the clearance lost time, l2, is
defined as the time interval between the last vehicle’s front
wheels crossing the stop line, and the initiation of the GREEN
for the next phase. The clearance lost time occurs each time a
flow of vehicles is stopped.
310

 Effective Green Time & Total Lost Time :
311
Displayed Green Time(G) Yellow AR (All Red)
Time
Flow
Rate
Effective Green time
(g)
Start-up
Lost time
(l1 )
Clearance
Lost time
(l2 )
Saturation Flow Rate

 Effective Green Time & Total Lost Time (cont.) :
312
)
(sec/phase
phase
per
time
lost
total
t
where
l
l
t
L
L


 2
1
 
(sec.)
(i)
movement
for
time
Lost
t
(sec.)
(i)
movement
for
times
Red
All
and
Yellow
AR
(Y
(sec.)
(i)
movement
for
time
green
Displayed
G
(sec.)
(i)
movement
for
time
green
Effective
g
where
t
AR
Y
G
g
L(i)
i
i
i
i
i
L
i
i
i
i









)
)
(

 Capacity of an Intersection lane or lane group:
The saturation flow rate(s) represents the capacity of an intersection lane or
lane group assuming that the light is always GREEN. The portion of real
time that is effective green is defined by the “green ratio,” the ratio of the
effective green time to the cycle length of the signal (g/C). The capacity of
an intersection may then be computed as:
313

 Capacity of an Intersection lane or lane group (cont.):
Determine the capacity for the given lane group at a signalized intersection:
Displayed Green Time (G) = 45 sec, Cycle Length (C) = 180 sec
Yellow + All Red times (Y+AR) = 6 sec
Average Saturation Discharge headway (h) = 2.8 sec
Start up lost time (l1) = 2.0 sec,
Clearance lost time (l2) = 1.0 sec,
ci = Si * gi/C = 1285 * 48/180 = 342.85 = 343 veh/hr
Si = 3600/h = 3600 /2.8 = 1285 veh/hr
gi + (l1+l2) = Gi + Yi +ARi
gi = 45 + 6 – (2+1) = 48 sec
314

Design and Analysis of Traffic Signals:
The Critical Lane and Time Budget Concepts
The Time Budget Concept:
 The time budget, is the allocation of time to various vehicular
and pedestrian movements at an intersection through signal
control. Time is a constant: there are always 3,600 seconds in
an hour, and all of them must be allocated. In any given hour,
time is “budgeted” to legal vehicular and pedestrian
movements and to lost times.
The Critical Lane:
 The “critical-lane,’ concept involves the identification of
specific lane movements that will control the timing of a given
signal phase.
315

The Critical Lane (cont.):
 In general, the following rules apply to the identification of critical
lanes:
(a) There is a critical lane and a critical-lane flow for each discrete
signal phase provided.
(b) Except for lost times, when no vehicles move, there must be one
and only one critical lane moving during every second of effective
green time in the signal cycle.
(c) Where there are overlapping phases, the potential combination of
lane flows yielding the highest sum of critical lane flows while
preserving the requirement of item (b) identifies critical lanes.
316

The Critical Lane (cont.):
 Example:
317
540 veh/ln
340 veh/ln
620 veh/ln
460 veh/ln
Phase 1 Phase 2

Signalized Intersection Capacity
The Maximum Sum of Critical-Lane Volumes: One View of Signalized
Intersection Capacity
The lost time per cycle (L) can be calculated as following:
The, the lost time per hour will be:
318

Intersection Capacity (cont.)
Then, the total effective green per hour TG will be:
TG =3600 - LH
This time may be used at a rate of one vehicle every h seconds, where h is the
saturation headway:
Then,
319
(sec./veh)
headway
n
Saturatio
-
h
(veh./hr)
volumes
lane
critical
of
sum
maximum
V
where
h
T
V
c
G
c








,
before
defined
as
avriables
all
where
C
t
N
h
V L
c
,
3600
*
3600
1















Intersection Capacity (cont.)
Then, the maximum sum of critical lane volumes (Vc) can be re-written as
following:
320




































C
t
N
S
V
then,
rate),
flow
n
saturatio
-
(S
C
t
N
S
V
C
t
N
h
V
L
c
L
c
L
c
*
1
*
1
*
1
3600

Minimum, Desirable and Optimum Cycle Length:
Based on the previous derivations for the maximum critical volume in the
intersection, then the Minimum Cycle Length will be:
321
length
cycle
minimum
the
is
this
S
V
t
N
C
S
V
C
t
N
C
t
N
S
V
then,
rate),
flow
n
saturatio
-
(S
C
t
N
S
V
c
L
c
L
L
c
L
c






































1
*
1
*
*
1
*
1
min

Minimum, Desirable and Optimum Cycle Length: (cont,)
intersection, then the Desirable Cycle Length will be:
322
ratio
capacity
to
volume
Desired
-
v/c
Rate
Flow
n
Saturatio
-
S
Factor
Hour
Peak
-
PHF
where
c
v
PHF
S
V
t
N
C
c
L
des










*
*
1
*

Minimum, Desirable and Optimum Cycle Length: (cont,)
intersection, then the Optimum Cycle Length will be:
Minimum cycle length: 60 sec
Maximum cycle length: 180 sec
In the past, cycle length was rounded to the nearest 5 sec. due to the design of
electromechanically dials.
323
 
 
phases
of
Number
-
N
phase
per
rate
flow
n
saturatio
to
volume
Critical
-
S
V
where
S
V
t
N
C
cr
cr
L
opt




1
5
*
*
5
.
1

‫ﺮﳼ‬

Traffic Signal Design: Step 0- Estimation of Saturation flow rate (S)
The saturation flow rate is either measured at the site as explained earlier or
estimated approximately using the HCM2000 method:
327

328

329

Traffic Signal Design: Step 1- Determine Phases
 For 4 legged intersection, the minimum number of phases is 2
& the maximum is 4
 Protected Left Turn Phase should be considered if any of the
following criteria is met:
1 more than one turning lane is provided
2 The LT demand volume is > 240 veh/hr
3 The cross product of LT demand & opposing TH is
>50,000 for one opposing TH lane
>90,000 for 2 opposing TH lane
>110,000 for 3 opposing TH lane
330

Traffic Signal Design: Step 2- Establish Analysis Lane Groups
 This process takes into consideration both the geometry of the
intersection and the distribution of the traffic movements. The
smallest number of lane groups is used that adequately
describes the operation of the intersection.
 Rules for lane groups are:
1- Movements from the same lane are considered as one lane
group.
2- Exclusive Left/Right Turn lanes are treated as a separate lane
group.
3- Judgment for shared movement lane(s).
331

Traffic Signal Design: Step 3- Determine Critical Lane Groups
 The critical lane group is the lane with the highest volume to saturation
flow rate ration (V/S) ratio in the same phase.
 Note: Allocation of Green time for each phase is based on the critical V/S
for each phase.
332

Traffic Signal Design: Step 4- Determine Change & Clearance
Intervals ( Y + AR) for each phase
 In this step, calculate the Yellow and All Red times for each
phase based on the critical movements using the following
equations:
 Estimate Start-Up & Clearance Lost Times (l1 & l2)
you may assume l1 = l2 = 2 sec.
 Estimate Lost time per phase : tL = l1 + l2
333





 

2
Speed
Passing
Speed
Approach
Distance
Sight
Stopping
Y
Speed
Passing
Length
Vehicle
Distance
Passing
AR



Traffic Signal Design: Step 5- Calculate Minimum Green Time
 For pedestrians to cross the intersection, the green time per-
phase, where pedestrians are allowed to cross the street, should
be sufficient to cross the intersection safely. The minimum
green time for pedestrians (Gp) is calculated as following:
 Then, the minimum displayed green per phase (Gmin) will be:
334
m/sec
1.3
)
Distance(m
Crossing
G
Speed
Walking
15%
Distance
Crossing
G
Time
Clearing
Ped.
Time
Intial
Ped
G
P
P
P






sec
5
sec
5
.
)
(
min AR
Y
G
G P 



Traffic Signal Design: Step 6- Calculate Optimum Cycle Length
 In this step, calculate the optimum cycle length:
Minimum cycle length: 60 sec
Maximum cycle length: 180 sec
 In cases of oversaturation: use the maximum cycle (180 sec.)
335
 
 
phases
of
Number
-
N
phase
per
rate
flow
n
saturatio
to
volume
Critical
-
S
V
where
S
V
t
N
C
cr
cr
L
opt




1
5
*
*
5
.
1

Traffic Signal Design: Step 7- Green Time Allocation
 In this step we shall allocate the effective green time for each
phase based on the critical V/S ratio for each phase.
336
 
phase
per
time
lost
Total
-
t
length
Cycle
-
C
phases
of
Number
-
N
(i)
phase
for
ratio
v/s
Critical
-
s
v
phase(i)
for
time
green
effective
The
-
g
where
t
N
C
s
v
s
v
g
L
i
cr
i
L
cr
i
cr
i
)
(
)
(
)
/
(
*
*
)
/
(
)
/
(




Traffic Signal Design: Step 8- Prepare Indication Diagram
 In this step we shall calculate the actual green time indicated for
each phase as following:
 Example:  
337
Intersection Layout
Phase 1
G1: 50 sec
Y+AR: 5 sec
Phase 2
G2: 79 sec
Y+AR: 5 sec
Phase 3
G3: 66 sec
Y+AR: 5 sec
W E
AR)
(Y
-
t
g
G i
L
i
i 



Traffic Signal Design: Example
For the shown T- intersection, adjusted traffic volumes are shown in the figure
below, then design the traffic signal.
Given:
STH = 2000 pc/hr/ln , SLT & SRT = 1000 pc/hr/ln ,
Right Turn on Red IS NOT ALLOWED
338
684 vph
200 vph
475 vph
185vph
165vph 330 vph
Intersection Layout Adjusted Flow rate for Lane Groups
W E

339

Traffic Signal HCM Level of Service Methodology:
340

Traffic Signal HCM Level of Service Methodology:
341

Traffic Signal LOS: Input Data
The needed data are the following:
 Traffic Volumes & PHF, %HV
 Lane Groups ( as in Traffic Signal Design)
 Signal Timing Information
 Saturation Flow Rate for each lane group
342

Traffic Signal LOS: Estimation of Saturation flow rate (S)
The saturation flow rate is either measured at the site as explained earlier or
estimated approximately using the HCM2000 method:
343

344

345

Traffic Signal LOS: Lane Groups
 This process takes into consideration both the geometry of the
intersection and the distribution of the traffic movements. The
smallest number of lane groups is used that adequately
describes the operation of the intersection.
 Rules for lane groups are:
1- Movements from the same lane are considered as one lane
group.
2- Exclusive Left/Right Turn lanes are treated as a separate lane
group.
3- Judgment for shared movement lane(s).
346

Traffic Signal LOS: Determining Delay
 Usually d3 is assumed to Zero
347

 Progression Adjustment Factor:
348

Traffic Signal LOS: Progression Factor
 Progression Adjustment Factor:
349

 Uniform Delay:
350

 Incremental (random) Delay:
 For Pre-timed Signals: k = 0.5
 For Isolated Intersection: l = 1.0
 Duration of Analysis : T= 0.25 hr
351

 Aggregated Delay Estimation:
352

Please note that the following problems are taken from the textbook “Traffic
Engineering” and they are in Imperial units and some of the problems address
issues that are not covered in this course!
Therefor, please contact me via (WhatsApp) if you have any question
regarding these problems: +966542328296

Capcity & LOS - 1

Capcity & LOS -2

Unsignalized Intersection 1

Unsignalized Intersection 2

Signal Timing & LOS 1

Traffic Signal Timing Design 1

Tteng 441 traffic engineering fall 2021 part5

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