ITE Journal April 2018 - 48

angles from crossroads to entrance ramps were verified to be
right angles. Based on methods from Wang et al., measurements
were conducted with measuring tools of Google Earth for each
study location and verified in field, including the turning radius
for left-turn drivers on crossroad, median type on crossroad, and
the median width between exit ramps and entrance ramps.12 In
addition, two lengths were measured, i.e. L1= the length from the
stop line of the left-turn lane(s) to the centerline of the median on
two-way ramps and L=the length of the entire intersection (the
distance between the stop lines in two opposite directions on the
crossroad). The stop line positioning through the intersection was
calculated by the following equation:12
L
S (%)= -1 * 100
L

Table 1. Analysis Results of Geometric Elements vs. WWD Crashes and ORs
(1)

WWD Crash Data
For WWD crashes in the selected sites, one crash database for
Illinois for a six-year period (2004-2009) was obtained from the
Highway Safety Information System (HSIS) of the Federal Highway
Administration (FHWA) that included crash coordinates and
wrong-way movement descriptions. Firstly, the route number,
roadway description, and roadway functional class of crashes
were used to verify the crashes were at interchange vicinities, with
street views and aerial photography Google Earth used as supplementary tools. Then, crash narratives were reviewed to confirm
that each crash resulted from WWD and to determine whether
the wrong-way entries occurred at interchange terminals. Thus,
wrong-way entry points for each crash were identified or estimated.

Based on the review of all hardcopy crash reports, 217 WWD
crashes were identified in total in the six-year period in Illinois,
fifteen of which occurred at signalized ramp terminals of parclo
interchanges, including confirmed and possible WWD entries.

Data Analysis
The effects of the existing applications of geometric elements were
analyzed for the 44 study sites. The frequency of WWD crashes
experienced at study sites was calculated for each technique. The
most common condition for WWD entries for each technique is
stop line positionings on crossroads more than 60 percent, turning
radii larger than 100 feet (ft), the traversable median, and medians
10 ft or less (See Table 1 column 3).

Furthermore, the Peto odds ratio (OR) assessed the contribution of several geometric elements and WWD using a 95
percent confidence interval as the relative measure at statistical
significance level of 0.05. This calculation is based on the null
hypothesis that treatment has no effect on outcome. Under
the null hypothesis, the difference between the observed and
the expected would have zero difference and variance. The
advantage of the OR approach over direct calculations is that
48

Ap r i l 2018

i te j o urn al

it allows for zero results without generating infinity, which is
suitable for some categories of variables in the dataset that have
no events. The OR value reflects the impact of a specific category
with larger numbers reflecting greater contribution. The results
were presented in Table 1. It reveals that WWD occurrences
increase when the stop line positioning on the crossroad is
more than 60 percent, the turning radius is larger than 80 ft, the
median is traversable, and the medians width is within 20-30 ft
between ramps. At statistical significance level of 0.05 (depicted
as red text in the table), significant differences exist between
different categories of each variable.

Variable

Category

WWD Crash
Odds Ratio
Frequency (%)

Stop Line
Positioning on
Crossroads

30%-40%

13.33

 1 (Reference)

40%-50%

6.67

0.24

50%-60%

20.00

0.46

More than 60%

60.00

5.24

50 ft. and less

6.67

1 (Reference)

Turning
Radius from
Crossroads

51 to 60 ft.

0.00

0.29

61 to 70 ft.

0.00

0.22

71 to 80 ft.

0.00

0.11

81 to 90 ft.

13.33

2.54

91 to 100 ft.

20.00

3.52

More than 100 ft. 60.00
Type of Median Non-traversable
on Crossroads Traversable
Median Width
between Exit
and Entrance
Ramps

1.79

33.33

1 (Reference)

66.67

1.39

10 ft. and less

33.33

1 (Reference)

10 to 20 ft.

26.67

0.17

21 to 30 ft.

20.00

3.85

31 to 40 ft.

20.00

3.11

41 to 50 ft.

0.00

0.49

51 to 60 ft.

0.00

0.15

More than 60 ft.

0.00

NA (Not
applicable)

Note: there is no interchange terminal with median widths on ramps more than 60 ft., hence "NA".

Conclusions and Recommendations
This paper summarizes the existing applications of geometric
elements that have been proposed to deter wrong-way movement
at parclo interchange terminals. It analyzed the collected WWD
crash and geometric design data to quantify the relationships
between geometric elements and WWD at parclo interchange



Table of Contents for the Digital Edition of ITE Journal April 2018

President’s Message
Director’s Message
People in the Profession
ITE News
Technical Programs Division Spotlight
Get Ready for Minneapolis!
Ethics Column: Responsible Engineer
Member to Member: Sammy Xiaoming Chen, Ph.D., P.E., PTOE, PTP
Where in the World?
Calendar
Industry News
New Products
Love My Hood: Kitchener’s Resident-Led Traffic Calming Program Advances Safety and Placemaking
Placemaking through a Traffic Signal Box Art Project: Effect of Artist Wrap to Cabinet Temperature
Shared Parking: Effective and Simple
Relationship between Geometric Elements and Wrong-Way Crashes at Partial Cloverleaf Interchange Terminals
Professional Services Directory
ITE Journal April 2018 - 1
ITE Journal April 2018 - 2
ITE Journal April 2018 - 3
ITE Journal April 2018 - President’s Message
ITE Journal April 2018 - 5
ITE Journal April 2018 - Director’s Message
ITE Journal April 2018 - 7
ITE Journal April 2018 - People in the Profession
ITE Journal April 2018 - 9
ITE Journal April 2018 - 10
ITE Journal April 2018 - 11
ITE Journal April 2018 - ITE News
ITE Journal April 2018 - 13
ITE Journal April 2018 - Technical Programs Division Spotlight
ITE Journal April 2018 - 15
ITE Journal April 2018 - Get Ready for Minneapolis!
ITE Journal April 2018 - 17
ITE Journal April 2018 - Ethics Column: Responsible Engineer
ITE Journal April 2018 - 19
ITE Journal April 2018 - 20
ITE Journal April 2018 - Member to Member: Sammy Xiaoming Chen, Ph.D., P.E., PTOE, PTP
ITE Journal April 2018 - 22
ITE Journal April 2018 - Calendar
ITE Journal April 2018 - New Products
ITE Journal April 2018 - 25
ITE Journal April 2018 - 26
ITE Journal April 2018 - Love My Hood: Kitchener’s Resident-Led Traffic Calming Program Advances Safety and Placemaking
ITE Journal April 2018 - 28
ITE Journal April 2018 - 29
ITE Journal April 2018 - 30
ITE Journal April 2018 - 31
ITE Journal April 2018 - Placemaking through a Traffic Signal Box Art Project: Effect of Artist Wrap to Cabinet Temperature
ITE Journal April 2018 - 33
ITE Journal April 2018 - 34
ITE Journal April 2018 - 35
ITE Journal April 2018 - 36
ITE Journal April 2018 - 37
ITE Journal April 2018 - 38
ITE Journal April 2018 - Shared Parking: Effective and Simple
ITE Journal April 2018 - 40
ITE Journal April 2018 - 41
ITE Journal April 2018 - 42
ITE Journal April 2018 - 43
ITE Journal April 2018 - 44
ITE Journal April 2018 - Relationship between Geometric Elements and Wrong-Way Crashes at Partial Cloverleaf Interchange Terminals
ITE Journal April 2018 - 46
ITE Journal April 2018 - 47
ITE Journal April 2018 - 48
ITE Journal April 2018 - 49
ITE Journal April 2018 - Professional Services Directory
ITE Journal April 2018 - 51
ITE Journal April 2018 - 52
http://www.nxtbook.com/ygsreprints/ITE/ITE_January2020
http://www.nxtbook.com/ygsreprints/ITE/ITE_December2019
http://www.nxtbook.com/ygsreprints/ITE/G110939_ITE_November2019
http://www.nxtbook.com/ygsreprints/ITE/G110110_ITE_October2019
http://www.nxtbook.com/ygsreprints/ITE/G110109_ITE_September2019
http://www.nxtbook.com/ygsreprints/ITE/G108559_ITE_August2019
http://www.nxtbook.com/ygsreprints/ITE/G108250_ITE_July2019
http://www.nxtbook.com/ygsreprints/ITE/G107225_ITE_June2019
http://www.nxtbook.com/ygsreprints/ITE/G104039_ITE_May2019
http://www.nxtbook.com/ygsreprints/ITE/G104038_ITE_April2019
http://www.nxtbook.com/ygsreprints/ITE/G104036_ITE_March2019
http://www.nxtbook.com/ygsreprints/ITE/G103582_ITE_February2019
http://www.nxtbook.com/ygsreprints/ITE/G102868_ITE_January2019
http://www.nxtbook.com/ygsreprints/ITE/G100155_ITE_December2018
http://www.nxtbook.com/ygsreprints/ITE/G100154_ITE_November2018
http://www.nxtbook.com/ygsreprints/ITE/G99495_ITE_October2018
http://www.nxtbook.com/ygsreprints/ITE/G98028_ITE_September2018
http://www.nxtbook.com/ygsreprints/ITE/G97366_ITE_August2018
http://www.nxtbook.com/ygsreprints/ITE/G96287_ITE_July2018
http://www.nxtbook.com/ygsreprints/ITE/G94315_ITE_June2018
http://www.nxtbook.com/ygsreprints/ITE/G93877_ITE_May2018
http://www.nxtbook.com/ygsreprints/ITE/G93065_ITE_Apr2018
http://www.nxtbook.com/ygsreprints/ITE/G91484_ITE_Mar2018
http://www.nxtbook.com/ygsreprints/ITE/G89434_ITE_Feb2018
http://www.nxtbook.com/ygsreprints/ITE/G86608_ITE_Jan2018
http://www.nxtbookMEDIA.com