Analysis of right-turn merging conflicts on channelized right-turn - - PowerPoint PPT Presentation

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Analysis of right-turn merging conflicts on channelized right-turn - - PowerPoint PPT Presentation

Mar 16, 2024 230 likes •511 views

Analysis of right-turn merging conflicts on channelized right-turn lanes at signalized intersections Presenter: Tim De Ceunynck (tim.deceunynck@uhasselt.be) Authors: Tim De Ceunynck, Stijn Daniels, Elke Hermans, Annelies Geussens, Tom Brijs,

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SLIDE 1

Analysis of right-turn merging conflicts

  • n channelized right-turn lanes at

signalized intersections

Presenter: Tim De Ceunynck (tim.deceunynck@uhasselt.be)

Authors: Tim De Ceunynck, Stijn Daniels, Elke Hermans, Annelies Geussens, Tom Brijs, & Geert Wets Hasselt University – Transportation Research Institute (IMOB), Belgium Aliaksei Laureshyn Lund University - Traffic & Roads, dpt. of Technology and Society, Faculty of Engineering LTH, Sweden

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SLIDE 2

Background

Channelized Right Turn Lanes (CRTL)

  • ften applied to improve mobility

Road designers believe they improve road safety However, little research about safety performance of right turn lanes (focus is usually on left turn lanes) Especially few guidelines about most appropriate type of traffic control at CRTL More research in this field needed

(Al-Kaisy & Roefaro, 2010)

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 3

Main research question?

Differences in safety performance between yield-controlled CRTL and signal-controlled CRTL?

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 4

Background

Features yield-controlled CRTL (YCRTL):

Avoids unnecessary waiting Road user needs to select own gap

Features signal-controlled CRTL (SCRTL):

Most interactions are separated in time Road user does not need to select a gap

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 5

Methodology

Semi-automated traffic conflict

  • bservation

Look at serious conflicts as surrogate for analysis of crash data

Steps:

1)Collect video data 2)Manual pre-selection of dangerous event 3)Software-assisted calculation of vehicle trajectories conflict indicators are measured in a more

  • bjective and reliable way than manual
  • bservation

(Laureshyn, 2010)

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 6

Methodology

  • 1. Collect video footage

2 intersections on ring road around Hasselt Very similar in lay-out and purpose in network; comparable AADT (but differences in volumes per direction)

Take volumes per direction into account when quantifying number of conflicts

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 7

Methodology

  • 1. Collect video footage (ct’d)
  • SCRTL = 2 lanes; YCRTL = 1 lane

in line with design guidelines (SCRTL) (YCRTL)

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 8

Methodology

  • 2. Manual pre-selection of dangerous events
  • 1 full week of video for each location is

viewed

  • All merging events that are considered

dangerous are selected (with large safety margin)

  • 3. Conflict severity measurement
  • Software-assisted estimation of road users’

trajectories

  • Automated calculation of time to collision

(TTC)

  • Calculation of TTCmin, Post Encroachment

Time (PET) and Time-to-Accident (TA)

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 9

Results

249 situations pre-selected and measured

SCRTL: 126 YCRTL: 123

Only severe situations included in further analysis

Selection criteria:

TA = serious (as defined by STCT)

SCRTL: 4 YCRTL: 10

TTCmin ≤ 2 sec

SCRTL: 19 YCRTL: 13

PET ≤ 1 sec (only in case of yield violation!)

SCRTL: 22 YCRTL: 29

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 10

Research question 1

QUESTION: Which type of CRTL leads to most dangerous situations? Simply compare the number of dangerous situations at each of both locations… …no?

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 11

Results

At which type do most serious conflicts

  • ccur?

Correct for exposure:

# right turning vehicles per week at SCRTL: 8 708 # right turning vehicles per week at YCRTL: 33 852

Χ²-test and adjusted standardized residuals applied TA value:

No significant difference in number of conflicts between both types

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

SCRTL YCRTL Serious conflicts 4 10 No serious conflicts 8.704 33.842 p-value 0,504

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SLIDE 12

Results

TTCmin and PET:

Proportion of conflicts is higher at SCRTL if we correct for the number of right turning road users

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

Absolute numbers Adjusted standardized residuals SCRTL YCRTL SCRTL YCRTL PET ≤1sec 22 29 4,0

  • 4,0

No PET ≤1sec 8686 33823

  • 4,0

4,0 p-value <0,001** Absolute numbers Adjusted standardized residuals SCRTL YCRTL SCRTL YCRTL TTCmin ≤2sec 19 14 5,3

  • 5,3

No TTCmin ≤2sec 8689 33838

  • 5,3

5,3 p-value <0,001**

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SLIDE 13

Results

2 out of 3 indicators indicate that relatively more right turning vehicles are involved in conflicts at the SCRTL Conclusion: SCRTL is more dangerous than YCRTL… … no?

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 14

Research question 2

QUESTION: With which type of conflicting traffic stream do most dangerous situations

  • ccur at each of both types of locations

EASY: Simply compare number of dangerous situations from each type that occur at both locations… … no?

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 15

Results

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

Serious TA conflicts

  • Adj. st. residuals

SCRTL YCRTL SCRTL YCRTL Straight through 8

  • 2,7

2,7 Left turn 2

  • 1,0

1,0 U-turn 4 3,7

  • 3,7

N (total) 4 10 p-value <0,001** PET close encounters

  • Adj. st. residuals

SCRTL YCRTL SCRTL YCRTL Straight through 6

  • 2,3

2,3 Left turn 1 21

  • 4,8

4,8 U-turn 21 2 6,3

  • 6,3

N (total) 22 29 p-value <0,001** TTCmin close encounters

  • Adj. st. residuals

SCRTL YCRTL SCRTL YCRTL Straight through 1 7

  • 3,1

3,1 Left turn 6

  • 3,3

3,3 U-turn 18 5,3

  • 5,3

N (total) 19 13 p-value <0,001**

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SLIDE 16

Results

Correct for exposure:

Exposure to number of vehicles from the conflicting direction is more relevant here

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

SCRTL YCRTL Straight through 35 604 63 937 Left turn 8 594 15 802 U-turn 1 365 168

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SLIDE 17

Results

Serious TA conflicts

  • Adj. st.

residuals SCRTL YCRTL SCRTL YCRTL Straight through Conflicts 8

  • 2,1

2,1 No conflicts 35.604 63.929 2,1

  • 2,1

p-value 0,057* Left turn Conflicts 2 No conflicts 8.594 15.802 p-value 0,544 U-turn Conflicts 4 No conflicts 1.365 168 p-value 1,000 TTCmin close encounters

  • Adj. st.

residuals SCRTL YCRTL SCRTL YCRTL Straight through Conflicts 1 7 No conflicts 35.603 63.930 p-value 0,730 Left turn Conflicts 6

  • 1,8

1,8 No conflicts 8.594 15.798 1,8

  • 1,8

p-value 0,097* U-turn Conflicts 18 No conflicts 1.351 168 p-value 0,248 PET close encounters

  • Adj. st.

residuals SCRTL YCRTL SCRTL YCRTL Straight through Conflicts 6

  • 1,8

1,8 No conflicts 35.604 63.931 1,8

  • 1,8

p-value 0,095* Left turn Conflicts 1 21

  • 3,0

3,0 No conflicts 8.593 15.783 3,0

  • 3,0

p-value 0,003** U-turn Conflicts 21 2 No conflicts 1.348 166 p-value 0,770

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SLIDE 18

Results

When we look at the proportions of dangerous situations of each intersection individually, we see that

At the SCRTL

U-turn conflicts are overrepresented for every indicator Conflicts with straight through traffic are less common than expected Inconclusive about conflicts with left turning vehicles

At the YCRTL

No significant difference in proportion of conflicts for TA values According to PET and TTCmin:

Overrepresentation of left turn conflicts Underrepresentation of straight through conflicts compared to contradicts with previous analysis that showed more straight through conflicts at YCRTL…?

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SLIDE 19

Results

HIDDEN

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

Serious TA conflicts SCRTL

  • Adj. st. residuals

Conflicts No conflicts Conflicts No conflicts Straight through 35.604

  • 3,8

3,8 Left turn 8.954

  • 1,0

1,0 U-turn 4 1.365 11,4

  • 11,4

p-value <0,001** YCRTL Conflicts No conflicts Straight through 8 63.929 Left turn 2 15.802 U-turn 168 p-value 1,000

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SLIDE 20

Results

HIDDEN

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

TTCmin close encounters SCRTL

  • Adj. st. residuals

Conflicts No conflicts Conflicts No conflicts Straight through 1 35.603

  • 7,7

7,7 Left turn 8.954

  • 2,1

2,1 U-turn 18 1.365 23,4

  • 23,4

p-value <0,001** YCRTL

  • Adj. st. residuals

Conflicts No conflicts Conflicts No conflicts Straight through 7 63.930

  • 2,4

2,4 Left turn 6 15.798 2,4

  • 2,4

U-turn 168

  • 0,2
  • 0,2

p-value 0,055*

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SLIDE 21

Results

HIDDEN

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

PET close encounters SCRTL

  • Adj. st. residuals

Conflicts No conflicts Conflicts No conflicts Straight through 35.604

  • 8,9

8,9 Left turn 1 8.953

  • 1,7

1,7 U-turn 21 1.348 25,4

  • 25,4

p-value <0,001** YCRTL

  • Adj. st. residuals

Conflicts No conflicts Conflicts No conflicts Straight through 6 63.931

  • 8,0

8,0 Left turn 21 15.783 7,1

  • 7,1

U-turn 2 166 7,9

  • 7,9

p-value <0,001*

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SLIDE 22

Discussion

Not all indicators are conclusive MORE conflicts at SCRTL according to TTCmin and PET

TTCmin and PET do not take speed into account at lower speeds, smaller time gaps can be expected when driving speeds are lower, MORE low TTCmin and PET values can be expected Composition of conflict types differs between both types of intersections

SCRTL has mainly U-turn conflicts lower conflicting speed than conflicts from other directions

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 23

Discussion

TTCmin

(in line with Archer, 2005) and PET seem unsuitable

for comparison between different types of conflicts

Lead to overrepresentation of low speed “conflicts”, which are relatively harmless, and can omit dangerous interactions at high speeds Therefore it seems doubtful to use them for cross-sectional comparison between locations with different features

So, does the higher number of TTCmin and PET conflicts at the SCRTL indicate a higher danger…?

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 24

Discussion

Use of the TA-value seems more valid than TTCmin and PET in this study

Includes driving speed in distinction between serious conflicts and non-serious conflicts Has been validated as surrogate for crash data, showing a fairly good correlation

(e.g. Chin & Quek, 1997; El-Basyouny & Sayed, 2013; Grayson et al., 1984; Hauer & Gårder, 1986; Hydén, 1987; Svensson, 1998;…)

Problem: very low number of records (4 resp. 10 in one full week of data)

Need for other conflict indicators:

More common, so conclusions can be based on more data Incorporate indicator of potential injury severity, rather than simply risk of colliding E.g. ΔV, which is determining factor for crash severity in accident reconstruction…?

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SLIDE 25

Conclusion

YCRTL have higher number of conflicts with straight through traffic

Can be more dangerous because of higher conflict speeds

SCRTL have fewer high speed conflicts, which can be beneficial for safety

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 26

Conclusion

SCRTL have a high number of conflicts with U-turning vehicles

Behavioural observations revealed that less right turning drivers look to their left when entering the intersection at the SCRTL

Do not expect to come in interaction with others Potential for occurrence of low severity crashes point of attention for road designers

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

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SLIDE 27

De Ceunynck, Daniels, Laureshyn, Hermans, Geussens, Brijs, & Wets

tim.deceunynck@uhasselt.be