Transcript Right-Turn Traffic Volume Reduction in Traffic Signal Warrant

Research Project for Nevada Department of Transportation
Right-Turn Traffic Volume Reduction in
Traffic Signal Warrant Analysis: A Delay Perspective
Presenter: Cui Zhou
University of Nevada, Reno
Center for Advanced Transportation Education and Research
March 27, 2014
Center for Advanced Transportation Education and Research
University of Nevada, Reno
1
Presentation Overview
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
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

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
Introduction
Previous Research
ITE Community Discussion
Problems in Existing Methods
Proposed Methodology
Case Study
Summary and Conclusions
Center for Advanced Transportation Education and Research
University of Nevada, Reno
2
Introduction

Importance of Traffic Signal Warrants
• What’s traffic signal warrants?
Standard: An engineering study of traffic conditions, pedestrian
characteristics, and physical characteristics of the location shall be
performed to determine whether installation of a traffic control
signal is justified at a particular location.
Center for Advanced Transportation Education and Research
University of Nevada, Reno
3
Introduction

Importance of Traffic Signal Warrants
• What’s traffic signal warrants?
Standard: An engineering study of traffic conditions, pedestrian
characteristics, and physical characteristics of the location shall be
performed to determine whether installation of a traffic control
signal is justified at a particular location.
• Consequences of an unwarranted signal
• Rear-end collisions
• Excessive delay and congestion
• Disobedience of signals
Center for Advanced Transportation Education and Research
University of Nevada, Reno
4
Introduction

Importance of Traffic Signal Warrants
• What’s traffic signal warrants?
Standard: An engineering study of traffic conditions, pedestrian
characteristics, and physical characteristics of the location shall be
performed to determine whether installation of a traffic control
signal is justified at a particular location.
• Consequences of an unwarranted signal
• Rear-end collisions
• Excessive delay and congestion
• Disobedience of signals
In short, traffic signals should be only installed when they will
alleviate more problems than they induce.
Center for Advanced Transportation Education and Research
University of Nevada, Reno
5
Introduction

Right-turn Traffic in Traffic Signal Warrants
Less operational
impact and faces fewer
conflicting vehicles
Make right turn
without the aid of
signals
Center for Advanced Transportation Education and Research
University of Nevada, Reno
High volumes of
right-turn traffic
can skew a signal
warrant analysis
and indicate an
incorrect need for
a signal
6
Introduction

Right-turn Traffic in Traffic Signal Warrants
Less operational
impact and faces fewer
conflicting vehicles
Make right turn
without the aid of
signals
Center for Advanced Transportation Education and Research
University of Nevada, Reno
High volumes of
right-turn traffic
can skew a signal
warrant analysis
and indicate an
incorrect need for
a signal
7
Introduction

Right-turn Traffic in Traffic Signal Warrants
Less operational
impact and faces fewer
conflicting vehicles
Make right turn
without the aid of
signals
High volumes of
right-turn traffic
can skew a signal
warrant analysis
and indicate an
incorrect need for
a signal
MUTCD and MTSD have clearly stated that some portion of the
right-turn traffic should be reduced from the minor street traffic count.
Center for Advanced Transportation Education and Research
University of Nevada, Reno
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Previous Research
Right-turn adjustments are usually based on engineering
judgment (EJ), field observation (FO), or an accepted right-turn
adjustment methodology (AM).
Center for Advanced Transportation Education and Research
University of Nevada, Reno
9
Previous Research
ITE Journal
• Mozdba et al.: adjusted in one of three conditions: accident
experience, sight distance obstruction and delay (EJ)
NCHRP
Report 457
• Right turns are reduced based on the conflicting volume. The
relationship is illustrated in a graph (AM)
DOT
Procedures
• Illinois: Pagones Theorem, which uses a minor-street
reduction and a mainline congestion factors to estimate the
right-turn volume (AM)
• Wisconsin: base on minor street geometry (EJ)
• Los Angeles: right-turn vehicles delayed less than 45s (FO)
• Oregon: right-turn lane or shared lane capacity (EJ)
• Arizona: right-turn experiencing a stopped-delay of five
seconds or less (FO)
Right-turn adjustments are usually based on engineering judgment (EJ), field
observation (FO), or an accepted right-turn adjustment methodology (AM).
Center for Advanced Transportation Education and Research
University of Nevada, Reno
10
ITE Community Discussion
Our topic was posted in the ITE community discussion section in
October 2013 and eight responses were received in this survey
Written
Policies
No Written
Policies
President of
Yarger
Engineering,
Inc
• Wisconsin and Illinois DOTs
• A consulting firm: NCHRP 457
• Federal Way: exclude right-turn volume if LOS was A
• Lee County(2): deduct left turns if there was a right-turn
lane
• Virginia DOT: Pagones Theorem
• A gray area and more guidance will be
helpful.
• Overrule included 100%, or on the other
side excluded all of the right turns
Center for Advanced Transportation Education and Research
University of Nevada, Reno
11
Problems In Existing Methods

Most of them are based on engineering judgments
Center for Advanced Transportation Education and Research
University of Nevada, Reno
12
Problem In Existing Methods

Most of them are based on engineering judgments

Pagones Theorem and NCHRP methods are relatively
sound
Center for Advanced Transportation Education and Research
University of Nevada, Reno
13
Problem In Existing Methods
Most
of them are based on engineering judgments
Pagones
Theorem and NCHRP method are relatively sound
• The intersection’s LOS after reduction is often one alphabet better
• Pagones Theorem fails to take into account the uneven volume
distribution
• The NCHRP method works out the reduction based on the
conflicting major-road. It doesn’t give any thought to the through and
left turn traffic
Center for Advanced Transportation Education and Research
University of Nevada, Reno
14
Methodology

The approach is based on delay equivalence
• Find the delay equivalent relationship between right-turn
and through traffic
é
3600 v ù
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ê
3600
v
v
c
cm ú
2
m
d=
+ 900T ê( -1) + ( -1) +
+5
ê cm
cm
cm
450T ú
ê
ú
ë
û
Center for Advanced Transportation Education and Research
University of Nevada, Reno
15
Methodology

The approach is based on delay equivalence
• Find the delay equivalent relationship between right-turn
and through traffic
é
3600 v ù
(
)( ) ú
ê
3600
v
v
c
cm ú
2
m
d=
+ 900T ê( -1) + ( -1) +
+5
ê cm
cm
cm
450T ú
ê
ú
ë
û
vc, t f , tc , f
Center for Advanced Transportation Education and Research
University of Nevada, Reno
16
Methodology

The approach is based on delay equivalence
• Find the delay equivalent relationship between right-turn
and through traffic
é
3600 v ù
(
)( ) ú
ê
3600
v
v
c
cm ú
2
m
d=
+ 900T ê( -1) + ( -1) +
+5
ê cm
cm
cm
450T ú
ê
ú
ë
û
vc, t f , tc , f

The estimation of control delay is implemented in
VBA programming in EXCEL according to HCM
2010
Center for Advanced Transportation Education and Research
University of Nevada, Reno
17
Methodology

An isolated intersection is studied
Directional ratio=
WB Volume: EB Volume
Center for Advanced Transportation Education and Research
University of Nevada, Reno
18
Methodology

An isolated intersection is studied

Five minor-street lane conditions are discussed
Condition
1
2
3
4
5
Lane
Configuration
Center for Advanced Transportation Education and Research
University of Nevada, Reno
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Condition 1

Different traffic volume scenarios are applied
(12,096 cases in total)
Mjr St.: 400, 500, 600, 700,
800, 900, 1000, 1100, 1200
vph
Direct. ratio: 1:1, 1:2, 1:3,
1:4, 2:1, 3:1, 4:1
Mnr St. RT: 50, 100, 150, 200,
300, 350, 400 vph
Mnr St. LT and T: 40, 60, 80, 100,
140, 160, 180, 200, 220, 240, 260,
300, 320, 340, 360, 380, 400, 420,
460, 480, 500 vph
Center for Advanced Transportation Education and Research
University of Nevada, Reno
250,
120,
280,
440,
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Condition 1

Different traffic volume scenarios are applied
(12,096 cases in total)
One Study
Situation
Mjr St.: 400, 500, 600, 700,
800, 900, 1000, 1100, 1200
vph
Direct. ratio: 1:1, 1:2, 1:3,
1:4, 2:1, 3:1, 4:1
Mnr St. RT: 50, 100, 150, 200,
300, 350, 400 vph
Mnr St. LT and T: 40, 60, 80, 100,
140, 160, 180, 200, 220, 240, 260,
300, 320, 340, 360, 380, 400, 420,
460, 480, 500 vph
Center for Advanced Transportation Education and Research
University of Nevada, Reno
250,
120,
280,
440,
20% LT
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Condition 1

Different traffic volumes scenarios are applied
(12,096 cases in total)
Mjr St.: 400, 500, 600, 700,
800, 900, 1000, 1100, 1200
vph
Direct. ratio: 1:1, 1:2, 1:3,
1:4, 2:1, 3:1, 4:1

Mnr St. RT: 50, 100, 150, 200,
300, 350, 400 vph
Mnr St. LT and T: 40, 60, 80, 100,
140, 160, 180, 200, 220, 240, 260,
300, 320, 340, 360, 380, 400, 420,
460, 480, 500 vph
250,
120,
280,
440,
The reduction factor could be calculated:
T2 - T1
f=
R
Center for Advanced Transportation Education and Research
University of Nevada, Reno
Radj = f ´ R
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Condition 1
The reduction factor graph in one specific study situation where the
mainline volume is 500 vph with 1:1 directional ratio
Center for Advanced Transportation Education and Research
University of Nevada, Reno
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Condition 1
The reduction factor graph in one specific study situation where the
mainline volumes are 500 vph with 1:1 directional ratio
Center for Advanced Transportation Education and Research
University of Nevada, Reno
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Condition 1

Reduction Factor Table
Center for Advanced Transportation Education and Research
University of Nevada, Reno
25
Condition 2

Using the same traffic volume scenarios, almost
the same reduction factors are obtained

From here, we could also see that the assumed
left-turn percentage doesn’t significantly affect
the equivalent results
Center for Advanced Transportation Education and Research
University of Nevada, Reno
26
Condition 3

20 left turns and zero through traffic are
assumed before reduction. The right-turn
movement volume is from 50 vph to 510 vph
with 20 vph increment

The adjusted minor street volume is the
maximum of adjusted right-turn and through &
left-turn traffic ( critical volume)
Center for Advanced Transportation Education and Research
University of Nevada, Reno
27
Condition 3

Reduction Factor Table
Center for Advanced Transportation Education and Research
University of Nevada, Reno
28
Condition 4

Minor street left-turn and through volume is from
40 vph to 700 vph with 20 vph increment
 Reduction factor graph when the mainline
volume is 500 vph.
Center for Advanced Transportation Education and Research
University of Nevada, Reno
29
Condition 4

Minor street left-turn and through volume is from
40 vph to 700 vph with 20 vph increment
 Reduction factor graph when the mainline
volume is 500 vph.
Center for Advanced Transportation Education and Research
University of Nevada, Reno
30
Condition 4

Reduction Factor Table
Center for Advanced Transportation Education and Research
University of Nevada, Reno
31
Condition 5

Because there is exclusive left-turn lane, left-turn
traffic is not considered in this condition.
 Reduction Factor Table
Center for Advanced Transportation Education and Research
University of Nevada, Reno
32
Case Study
26 intersections’ turning volumes provided by
NDOT
 According to 8 hour warrant in MUTCD, divide
these cases into three categories:

• warrant meets without right turning (7 cases) ;
• warrant doesn’t meet with all turning movement (12
cases);
• warrant meets when considering all turning movement
(7 cases)
Center for Advanced Transportation Education and Research
University of Nevada, Reno
33
Case Study
26 intersections’ turning volumes provided by
NDOT
 According to 8 hour warrant in MUTCD, divide
these cases into three categories:

• warrant meets without right turning (7 cases) ;
• warrant doesn’t meet with all turning movement (12
cases);
• warrant meets when considering all turning movement
(7 cases)
Center for Advanced Transportation Education and Research
University of Nevada, Reno
34
Case Study: Lamoille Hwy and Spring Creek Pkwy
Lamoille Hwy
Spring Creek Pkwy
Center for Advanced Transportation Education and Research
University of Nevada, Reno
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Case Study: Lamoille Hwy and Spring Creek Pkwy
Center for Advanced Transportation Education and Research
University of Nevada, Reno
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Case Study: US395 and Airport Rd
Airport Rd
Center for Advanced Transportation Education and Research
University of Nevada, Reno
US395
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Case Study: Lamoille Hwy and Spring Creek Pkwy
Center for Advanced Transportation Education and Research
University of Nevada, Reno
38
Summary and Conclusions

Unwarranted traffic signals are detrimental
Center for Advanced Transportation Education and Research
University of Nevada, Reno
39
Summary and Conclusions


Unwarranted traffic signals are detrimental
Engineers agree on reducing right-turn volumes, but
there is no mature guidance
Center for Advanced Transportation Education and Research
University of Nevada, Reno
40
Summary and Conclusions



Unwarranted traffic signals are detrimental
Engineers agree on reducing right-turn volumes, but
there is no mature guidance
This paper proposed a new guideline which is based
on the equivalent relation when right turns and through
traffic achieve the same delay
Center for Advanced Transportation Education and Research
University of Nevada, Reno
41
Summary and Conclusions




Unwarranted traffic signals are detrimental
Engineers agree on reducing right-turn volumes, but
there is no mature guidance
This paper proposed a new guideline which is based
on the equivalent relation when right turns and through
traffic achieve the same delay
Five conditions are divided, and further 63 study
situations are provided in each condition
Center for Advanced Transportation Education and Research
University of Nevada, Reno
42
Summary and Conclusions





Unwarranted traffic signals are detrimental
Engineers agree on reducing right-turn volumes, but
there is no mature guidance
This paper proposed a new guideline which is based
on the equivalent relation when right turns and through
traffic achieve the same delay
Five conditions are divided, and further 63 study
situations are provided in each condition
Case studies were conducted. The proposed guideline
can easily help engineers make sound decisions for
the adjustment of right turns
Center for Advanced Transportation Education and Research
University of Nevada, Reno
43
Thank you for listening!
Center for Advanced Transportation Education and Research
University of Nevada, Reno
44