A Surrogate Safety Assessment of Scrambled Phase Intersections

• Author / Creator

  Ghaneei, Zakiye

• Since traffic safety is a significant concern for policymakers and researchers, multiple studies have been conducted to address this issue and create a safer environment for all road users, especially pedestrians. One of the approaches to achieving this is installing scramble phases at intersections with high volumes of vulnerable road users. This research evaluated the safety impact of installing the scramble phase at the two intersections in Edmonton, Canada, over three periods. The first observation was made before the installation of the scramble phase, followed by observations immediately after the installation, and finally, after six months of installation. The research utilized two approaches to evaluate the safety impact of the scramble phase installation. The first approach was to observe the frequency of right-turn-on-red violations. The second approach involved investigating the frequency of serious conflicts before and after the installation using three safety indicators, namely, Time to Collision (TTC), Time Difference to Point of Intersection (TDPI), and Distance between Stop Position and Pedestrian (DSPP). The number of breaches before and after the installation was counted manually to evaluate the frequency of right-turn-on-red violations. The results showed a decrease in the total number of right-turn-on-red violations after the implementation during the six months. However, there was a slight increase in violations during the pedestrian phase at one intersection after six months. The research used conflict detection and automatic indicator calculations to assess the frequency of serious conflicts. The results showed a 65% decrease in all three safety indicators immediately after the installation of the scramble phase at the Calgary trail intersection. Furthermore, after six months, there were no incidents of DSPP and TDPI at this intersection. At one of the study intersections, there was also a reduction in serious conflicts, although it was less than 50% immediately after the installation. However, this improvement increased to 80% for all indicators after six months. Reduced severe conflicts and total right-turn-on-red violations indicate that installing the scramble phase positively impacted intersection safety.

• Subjects / Keywords

  • Road Safety
  • Scrambled Phase
  • Conflict Analysis
  • Surrogate Safety Measure

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-g5n3-aj29

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.