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									Zhong et al                       3rd Urban Street Symposium                                 1
                              June 24-27, 2007 Seattle, Washington

Study on the Relationship of Intersection Design and Safety of Urban

                         Unsignalized Intersection in China


                                                              Liande Zhong
Authors:
                                                              Ph.D. Student
       Xiaoming Zhong, Ph.D., P.E.
                                                    Beijing University of Technology
    Chelbi Engineering Consultant, Inc.
                                                              Xinzheng Zhu
 No.20, Anyuan Road, 8 Floor - Xingyuan
                                                              Master student
      Talent Tower, Chaoyang District
                                                    Beijing University of Technology
                 Beijing, China
                                                                  JiaJia
               Post code: 100029                   Chelbi Engineering Consultant, Inc.
        Tel: 86-10-84868688-8015,
                                                               Ming Zhao
              Fax: 86-10-84896981
                                                   Chelbi Engineering Consultant, Inc.
        2005.xiaoming@gmail.com

        Zhong_xiaoming@126.com                           Jianming Ma , Ph.D.
                                                    The University of Texas at Austin.
                                                    6.9 E. Cockrell Jr. Hall, Austin, TX
     Yuanyuan Wang, Master Student
                                                               78712-1076
     Beijing University of Technology.

    100 Pingleyuan, Chaoyang District
                                                       Xiaoming Liu, Professor
                 Beijing, China
                                                    Beijing University of Technology.
               Post code: 100022
                                                100 Pingleyuan, Chaoyang District, Beijing
              yuanyuanws@sina.com
                                                              100022, China




Submitted for Presentation and Publication Consideration at 3rd Urban Street
             Symposium of the Transportation Research Board
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                           June 24-27, 2007 Seattle, Washington




     Abstract: Unsignalized intersections with yield control or stop signs on the
minor roads are one of the most common intersection types in the urban street systems
in China. Good intersection design will promote traffic safety and efficient traffic
operation. A poorly-operated unsignalized intersection may also cause serious traffic
safety problems. Statistical crash data showed that in China 13,529 fatalities occurred
at unsignalized intersections in 2005. Although lots of good safety design measures
have been used to improve intersection safety and operation in recent years, some of
them were not targeted at the safety problems and thus had little or negligible effects.
However few researchers have explored the relationship of intersection design and
safety in China.
     The objective of the paper was to identify the relationship of intersection design
and the main crash reasons. Field studies were conducted at 96 selected intersections
with yield control or stop signs on the minor roads to evaluate the safety design in
Beijing’s urban streets. Nearly 410 crashes, occurring at these intersections in the last
three years, were analyzed in detail in the paper. The behaviors of the road users
(including drivers, bicyclists and pedestrians) were observed in different safety
designs, which implied the relationship of intersection design and safety on urban
streets. Based on the findings of crash reasons and defects of safety designs, the paper
discussed some practical countermeasures to safety design for urban unsignalized
intersections in China.
    Keywords: Traffic safety; Intersection design; Unsignalized Intersections; Road

users’ behaviors, design defect
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INTRODUCTION


     Unsignalized intersections with yield control or stop signs on the minor roads are
one of the most common intersection types in the urban street systems in China. Good
intersection design combined with good traffic control will promote traffic safety and

efficient traffic operation(1, 3) A poorly-operated unsignalized intersection may
                              2, .

also cause serious traffic safety problems. It is not unusual that crashes are
concentrated at intersections, because intersections are the point on the roadway
system where traffic movements most frequently conflict with one another.
     The relationships between intersection safety and operation have been studied in
recent years (3, 5, 6, etc.). Lots of good safety design measures have taken into
practice and achieved great safety benefits. However, some of safety design measures
were not targeted at the safety problems and thus had little or negligible effects in
China. Statistical crash data showed that 13,529 fatalities occurred at unsignalized
intersections which accounted for 13.7 percent of the total deaths in 2005 in China(7).
However few researchers have explored the relationship of intersection design and
safety in China.
     The objective of the paper was to identify the relationship of intersection design
and the main crash reasons. Field studies were conducted at 96 selected intersections
with yield control or stop signs on the minor roads to evaluate the safety design in
Beijing’s urban streets. Nearly 410 crashes, occurring at these intersections in the last
three years, were analyzed in detail in the paper. The behaviors of the road users
(including drivers, bicyclists and pedestrians) were observed in different safety
designs, which implied the relationship of intersection design and safety on urban
streets. Based on the findings of crash reasons and defects of safety designs, the paper
discussed some good practical countermeasures to safety design for urban
unsignalized intersections in China.
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DATA COLLECTION


     It was selected 96 sample intersections with yield control or stop signs on the
minor roads to in Beijing’s urban streets in 2007. The main purpose of the site visit is
to gain a first-hand appreciation of the physical and operational conditions of these
intersections. The site visit is an opportunity for the analysts to have a detailed look at
the high crash risk location. Intersection data collected including:
    Crash data from 2004 to 2006
    Geometric design characteristics: design speed, intersection angle, horizontal and

    vertical alignment of approaches, cross slopes / superelevation,width of lane,

    number of lane, drainage, curb, crosswalks ,sidewalk, left-turn or right-turn

    lane ,auxiliary lanes etc.

    Traffic engineering design characteristics: posted speed, sign, pavement mark,

    channelization features,delineation, speed control, refuge island;

    Road Surface characteristics: Skid resistance, Pavement Distress (i.e., potholes,
    rutting, etc.), Surface Texture (Visibility in wet conditions or sunlight conditions)
    Traffic design: congestion areas, pedestrian and bicycle and driver behaviors,
    function of the intersection, design vehicles

    Environment design characteristics: weather, information, sight distance, street

    parking, illumination, roadside development


DATA ANALYSIS


Characteristics of Crash Type and Manner of Collision

     There were 409 traffic crashes occurred at sample intersections (The details of
crash was shown in Table 1). The number of single-vehicle crash was 34 while the
number of multiple-vehicle was 235 respectively, caused 36 fatalities and 223 people
injured. It was noticeable that the pedestrian and cyclist crashes accounted for 34.23%
of the total crashes whereas theses crashes killed 35 people and took up about 50
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percent of the total fatalities. It implied that the safety of pedestrians and cyclists
should be attached importance to when making safety policies of intersections.
                       TABLE 1       Crash Type Statistical Characteristics

                               Percentage                Percentage    Number    Percentage   Number of
                    Number                  Number of
   Crash type                   of total                  of total       of       of total    intersections
                    of crash                fatalities
                                crashes                   fatalities   injures    injures       involved

 Multiple-vehicle
                      235       57.46%         33         46.48%        196       59.57%           76
      crash

  Single-vehicle
                      34         8.31%          3          4.23%         27        8.21%           22
      crash

 Pedestrian crash     65        15.89%         21         29.58%         44       13.37%           30


  Cyclist crash       75        18.34%         14         19.72%         61       18.54%           34


      Total           409      100.00%         71        100.00%        329      100.00%           --



     As was shown in Table2 and the pie graph of characteristics of crash types and
manner of collisions (Figure 1), three types of crash( side collision, sideswipe and
rear-end collision ) were most common type of multiple-vehicle crash, and took up
47% of the total crashes. The type of collision with pedestrian and bicycle shared a
great portion, as a 34 percentage of total crashes.
     The type of head-on collision and pedestrian crash were the most dangerous
crashes, which would cause more than thirty people dead and seventy people injure if
there had happened 100 crashes.
     If crashes always occur in a certain intersection, it hints there is something wrong
with the intersection design or control tactics. If some countermeasures has been
introduced during intersection rebuilt project, it means the countermeasures may not
target at the safety problems and thus has little or negligible effects.
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                  ol           i
                 C l i si on w t h          ol             i
                                           C l i si on w t h            Si de col l i si on
                     cycl i st                 pedest r i an                   25%
                        18%                       16%                                         Rear end
                                                                                              col l i si on
                                                                                                  12%


                                                                                                       i
                                                                                              Si desw pe
                                                                                                  sam e
        C l i si on w t h
         ol            i                                                                      di r ect i on
                                                                                              col l i si on
              par ked
                                                                                                   10%
            vehi cl es
                1%                                                                                      i
                                                                                               Si desw pe
                                                                Head on                        opposi t e
                                       ol          i
                                      C l i si on w t h
        O t ur ned
         ver                                                   col l i si on                   di r ect i on
                                      f i xed obj ect s
             2%                                                     2%                         col l i si on
                                             5%
                                                                                                     9%

       FIGURE1              Characteristics of Crash Type and Manner of Collision


                            TABLE 2        Crash Type and Manner of Collision



                                                                                                    Severity level

                                                  Number                           Number                      Average
                              Manner of                         Number of                       Average        number
    Crash type                                       of                               of
                              Collision                          fatalities                    number of          of
                                                  crashes                          injures
                                                                                              fatalities of    injures
                                                                                                a crash          of a
                                                                                                                crash

                             Side collision          98               19               79          0.19         0.81


                               Rear end
                                                     49               11               38          0.22         0.78
                               collision

                            Sideswipe same
 Multiple-vehicle              direction             42                0               39          0.00         0.93
      crash                    collision
                              Sideswipe
                               opposite
                                                     37                0               34          0.00         0.92
                               direction
                               collision
                               Head on
                                                      9                3                6          0.33         0.67
                               collision
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                 TABLE 2     Crash Type and Manner of Collision( continuous)



                                                                                Severity level

                                         Number                  Number                    Average
                          Manner of                Number of                 Average       number
    Crash type                              of                      of
                          Collision                 fatalities              number of         of
                                         crashes                 injures
                                                                           fatalities of   injures
                                                                             a crash         of a
                                                                                            crash

                      Collision with
                                           19          0           16          0.00         0.84
                      fixed objects
  Single-vehicle
      crash               Overturned       10          2           7           0.20         0.70
                      Collision with
                                            5          1           4           0.20         0.80
                      parked vehicles
                      Collision with
   Cyclist crash                           75          14          61          0.19         0.81
                         cyclist
                      Collision with
 Pedestrian crash                          65          21          44          0.32         0.68
                        pedestrian
   Total of
Multiple-vehicle
crash and                                  409         71         139          0.17         0.34
Single-vehicle
crash



Main causes of crash

     Many factors contribute to traffic crashes, such as driving skill and experience,
driver attitudes to safety law, vehicles performance, roadway and roadside conditions,
geometric design deflection, bad weather, etc.
     According to the statistical analysis of crashes ( Figure 2) , there were six main
causes of cashes, i.e. disobeying the rule (or law) of yield, accounted for about 26.37
percent of total crashes; driving operational errors and speeding caused 15.49 to 11.69
percent of all crashes; fail to keep safety distance led to 8.92 percent of all crashes;
illegal turning operation took 5.25 percent of the total; bicycle and pedestrian risk
behaviors (such as dash and suddenly turning) involved in approximately 11.45
percent of all crashes.
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     However, the six main causes mentioned above are associated with intersection
design, enforcement and education programs of traffic safety. Because design defect
may induce more dangerous and risk behavior of road users, the paper would be focus
on some safety treatments of intersection design.


                                      30.00%          Motorist disobey
                                                      the rule of yield ,
                                                           26.37%
                                      25.00%
                                                               Driving error
              Percentage of crashes




                                                              /Misoperation ,
                                      20.00%                      15.49%
                                                                                 Speeding ,
                                      15.00%                                      11.69%
                                                                                       Illegal turn-    Fail to keep
                                                                                    operation, 9.32% distance , 8.92%
                                      10.00%
                                                                                                                                           Bycycler risk-behaviors( fail
                                                                                                                                                to yield), 5.75%
                                                                                                                                                                     Pedestrian risk behavior( fail
                                                                                                                                                                          to yield), 5.71%
                                      5.00%




                                      0.00%
                                                   Motorist      Driving error   Speeding   Illegal turn-   Fail to keep   Pedestrian risk Bycycler risk-          Illegal       Dad vehicle   driving after unexpected risk Illegal driving Illegal to turn Fatigue driving Illegalto back
                                               disobey the rule /Misoperation                 operation      distance      behavior( fail to behaviors( fail    operation of                       drink                      on a opposite      around                       one's vehicle
                                                   of yield                                                                    yield)           to yield)        overtaking                                                     direction
                                                                                                                                                               another vehicle




                                                                                                                      Main Causes of crashes



                                                    FIGURE2                                        Main Causes of Crashes


Typical Design defects of intersection in China

     Any design defects are a potential risk for road users. It was found some different
geometric design defects, traffic engineering design defects, traffic design defects and
environment design defects in some intersections, which may contribute to traffic
crashes. Most typical design defects of intersection found in samples would be
illustrated as follows.

Defects of Geometric design

     The skew angle of an intersection is contributing to collisions( 3,4,8). The degree
of the acute angle is smaller, and the danger of the intersection is higher. It was found
the number of traffic crashes occurred at intersections with sharp angles was two to
three times higher than that of traffic crashes occurred at intersections with
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right-angles. Field data showed these intersections usually experience two problems:
The drivers’ field of view and sight angle for observation of opposing traffic and
pedestrian crossing is decreased. Drivers making right turns around an acute-angle
radius may encroach on lanes intended for oncoming traffic from the right. The study
results revealed that reducing or eliminating the skew angle of an intersection is
helpful to improve traffic safety.
     The improper combination of horizontal and vertical alignment of approaches
may increase the frequency and severity of intersection conflicts(3,4,9). Field study
shown the accident rate was high when alignment of intersection approaches is sharp
curve or steep grade or the combination of vertical and horizontal. These intersections
usually experience the follow problems: Sharp horizontal curves or excessive grades
usually cause sliding in adverse weather conditions; sharp horizontal and vertical
curves usually interfere with or restrict sight distance along approaches. Sharp
horizontal curves or excessive grades usually cause drivers’ driving errors once the
emergent incident happen. The study indicated that improving the alignment of
approaches would provide safe operating condition.
     Large intersection does not provide exclusive left-turn or right-turn lane, which
lead to many collisions (10). Large intersections have been appeared since many
two-lane roads have been rebuilt into multiple-lane roads. Many conflict points are
produced by left-turn and right-turn maneuvers in multiple-lane intersection area.
Collisions at unsignalized intersection are related to turning maneuvers. Exclusive
left-turn or right-turn lanes remove vehicles waiting to turn from through-traffic
stream and provide a sheltered location for drivers to wait for a adequate gap to
complete the turning maneuver, thus reducing the potential for rear-end collision (5,
6). Though some exclusive turn lanes installed at some large intersections, safety
benefits lost because unreasonable exclusive lanes are designed (such as inadequate
length of left-turn or right-turn lane to accommodate vehicle deceleration and storage,
particularly on high-volume and high-speed major road approach.) in recent years.
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Defects of Traffic engineering design

     Setting inadequate or unreasonable traffic engineering facilities often leads to an
increased frequency of crashes. These defects including:
Markings:      Worn pavement markings are not clearly visible in day and night time.
New pavement markings confuse drivers or lead to erratic behaviors when old
markings have not removed. Some roads lack of zebra markings for cyclists and
pedestrians.
Signs: Overload information is given and confuse drivers when many signs appear at

the same time or locate at one pole. Posted speed sign is not reasonable and cause
some motorists unsafe behaviors ( e.g. speeding).     Visibility and readability of signs
is not suit for approaching users. Location of signs is not appropriate (i.e., proper
height, offset, distance in advance of hazard are ignored). Signs usually are redundant,
missing or broken.
Delineation: Delineation is not adequate or effective in all conditions. Retro-reflective

devices intended for heavy vehicle operators below the drivers’ eye height. Improper
grades of retro-reflective sheeting are used.

Defects of Non-Motorized Traffic facilities design

     Mixed traffic problem is the most typical and most difficult problem for traffic
engineers in China. Some cyclists and pedestrians don’t comply with the Road Safety
Law and most large intersection do not provide non-motorized traffic facilities for
vulnerable road users ( e.g. crossing island, refuge area, pedestrian signals, bicycle
lane). In addition, some non-motorized traffic facilities do not use correctly. For
example, marked crosswalk is not installed at locations that may pose unusual safety
risks to pedestrian. Marked crosswalk is provided alone and lacks of other safety
treatments ( e.g. raised medians, speed humps, traffic-claming, lighting, traffic
signals).
     Although some other common defects are found in the field survey, but the
defects mentioned above are the most typical defects.
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COUNTERMEASURE OF INTERSECTION SAFETY DESIGN PRACTICE IN

CHINA

     The design of unsignalized intersections is frequently complex and problematic,
requiring the designer to examine and respond to many different factors and issues. To
design intersections that are both functional and safety effective, designers need
current information regarding intersection design that is easily accessible and in a

user-friendly format (2,5,11, 12, 13).

     After scanning innovative safety practices of China and abroad( including USA,
Sweden, Germany and the United Kingdom), a lot of countermeasures and good
suggestions to alleviate the potential problems of design defects are found in the
literates (such as FHWA “urban intersection design guide: volume 1 – guidelines”

(1);FHWA “innovative intersection safety improvement strategies and management

practices: a domestic scan”(2);“the fifth volume of the NCHRP report 500volume 5:

a guide for addressing unsignalized intersection collisions”(5); “Florida intersection
design guide for new construction and major reconstruction of at-grade intersections

on the state highway system”(9); FHWA “pedestrian facilities users guide –

providing safety and mobility”; “signalized intersection safety in Europe”(11)).

     Here the authors will not repeat those theories or principles of unsignalized
intersection safety design. But the authors are interested in “What we have done
recently in China?”, which may be concerned by other friends abroad.             Some
technology have been updated or adapted to traffic characteristics of China paper will
be discussed in following paragraphs.
     (1)      Making pavement markings visible clearly and improving retro-reflectivity
performance of pavement markings
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FIGURE 3       Effective Channelization And Good Retro-Reflectivity Performance


     (2)Adding delineation facilities near intersection and marked to warn road

users




        FIGURE 4    Delineation Facilities and Hazardous Object Protection


(3)Using facilities to limit some heavy truck beyond the warrant (overloading,

excess-size heavy truck) and traffic calming treatments( such as installing speed
hump)




Figure 5      Facilities To Limit Some Heavy Truck Beyond The Warrant And
                            Facilities of Speed Hump
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(4) Raising medians and setting crossing islands to improve pedestrian safety




   Figure 6     Raised Medians and Crossing Island (Pedestrian Refuge Island)


     (5)Supplement pedestrian warning signs and extended curb at intersections to

shorten the crossing distance




              Figure 7     Pedestrian Warning Signs and Extended Curb


     (6)Building pedestrian overpass or tunnel and installing bike lanes to protect

pedestrians and cyclists




Figure 8      Pedestrian Overpass Sign (or Pedestrian Tunnel Sign) And Bike Lane
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     ( 7 ) Changing unsignalized intersections into signalized intersections and

providing exclusive left- turn or right-turn lane and related signal phasing




Figure 9      Signalized Intersection And Providing Exclusive Turn Lane To
                           Improve Safety
     (8)Providing pedestrian and cyclist signals where traffic volume is high when

changing unsignalized intersections into signalized intersections




                  Figure 10    Signals For Pedestrians and Cyclists


Conclusion

     This paper discussed the relationship of intersection design and safety of urban
unsignalized intersections in China. The objective of the paper was to identify the
relationship of intersection design and the main crash reasons. Based on the crash
analysis of sample, it concluded:
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                             June 24-27, 2007 Seattle, Washington

          Characteristics of crash type and main causes of collisions of unsignalized
          intersections in China
          Typical design defects of unsignalized intersection involved defects of
          geometric design, traffic engineering design and non-motorized traffic
          facilities design in China
          Some useful countermeasure of intersection safety design practice for mixed
          traffic of China


Acknowledgements

     The authors wish to express special gratitude to Professor Xiaoduan Sun,
Associate Professor Yongsheng Chen, Yong Zhang, Li Zhang, Jie Zhang, Qiushi Xu,
Guoping Sun, Xinzheng Zhu, Jianhua Xie, Dehui Li, and Rui Sun for their kind help.
     And special thanks to for Dr. Jill Graham.
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