IMPROVEMENT OF TRAFFIC SIGNAL CONTROL STRATEGY LHOVRA

1
IMPROVEMENT OF TRAFFIC SIGNAL CONTROL STRATEGY
LHOVRA

• Azhar Al-Mudhaffar
• Transport and Logistics,
• Transport and Economics, KTH

2
Isolated signal control with the LHOVRA technique

• LHOVRA was originally developed in order to
  increase safety and to reduce lost time and the
  number of stopped vehicles at signalized
  intersections along high-speed roads, During
  its trial period, the accident rate at the test
  intersections reduced from 0.7 to 0.5 accidents
  per million incoming vehicles

3
The LHOVRA acronym and detector positions
4
The incident reduction function

• The O function is intended to reduce the number
  of vehicles in the option zone and thereby
  reducing the number of red light drivers and
  rear-end collisions, by extending the green time
  known as Past-end green

5
Option zone
6
Option zone

7
Past - end green
8
Evaluation and development

• Three different studies
• Theoretical analysis
• Field measurements
• Micro simulation

9
Theoretical analysis Discussion points

• Green time extension based on existence of only
  one vehicle in the option zone
• Detector locations designed for 70 km/h or higher
  speed vehicles
• May have opposite effect for vehicles driving at
  lower speeds

10
(No Transcript)
11
(No Transcript)
12
Suggestions for improvement

• Changing detector location and green time
  extension
• Using double-loop detector (or video sensors) at
  beginning of the option zone to measure speeds
• Considering the headway between two vehicles in
  the option zone

13
Considering the headway

• The condition is if the headway between the
  existing vehicle and the new approached one is
  less than (detector distance to the stop line -
  min possible stop distance of existence vehicle)
  / speed, then an order of extension must be given
  

14
(No Transcript)
15
(No Transcript)
16
Field Measurements Methods of data collection

• Ø Two digital cameras on a Tower.
• Ø Signal Controller output recorded
• Ø Pneumatic tubes in the same location of the
  normal detectors.
• Ø All connected to one data-logger for time
  synchronisation

17
Results of the field measurements

• The average of the reaction time is about 1
  second while the LHOVRA handbook assumes that it
  is 0.75 second
• The max deceleration is 4.6 m/s2 while the LHOVRA
  handbook assumes that it is 4.9 m/s2
• Results of from Ängbyplan are as follows
•  
• The data collection corresponds to Ängbyplan at
  the interval 730-750. The number of observation
  was 20 and the average speed was 66.5 km/h.

18
Stop and go behavior in reaction to amber
19
Practical option zone

• Real speed range and practical option zone in the
  approaches with 50 km/h posted speed

20
Stopped vehicles

• The share of the stopped vehicles after receiving
  past-end green (PEG)

21
Simulation Choosing a model

• VISSIM was selected as the model of
  choice possible to define behaviour in
  relation to the onset of amber (reaction-to-amber
  ) possible to program LHOVRA functions in
  the VisVAP module

22
Intersection test site
23
Calibration Driver Decision modelling

• One decision model
• Logistic function with three parameters
• Two variables Speed and Distance

24
Driver decision modelling

• Binary logistic regression used to estimate the
  three parameters from the field data
• Results of the stop probability from the field
  have given softer curves than these used in VISSIM

25
Simulation Experiment

• 4 Scenarios
• Detector positions 1. 130 and 80 metres
  (standard) 2. 110 and 65 metres (suggested)
• Signal controller logic
• 1. Standard O function
• 2. Speed dependent O function

26
Results
27
Conclusions

• A speed dependent O function-reduces wasted
  green time and number of stops after receiving
  PEG,-has a positive effect on safety in the form
  of a reduction in measures of TTC
• A distance closer to the stop line reduces
  red-light violations.

28
Future research

• Simulation tests of other models based on newly
  collected field data to optimize detector
  position
• Field tests.

29

• THANK YOU FOR YOUR ATTENTION