Evaluation of Effectiveness of Automated Workzone Information Systems

1University of California

IrvineUniversity of California



Irvine

Evaluation of Effectiveness of Automated Workzone Information Systems

Lianyu Chu CCIT, University of California Berkeley

Hee-Kyung Kim, Yonshik Chung, Will ReckerUniversity of California Irvine





Irvine

OUTLINE

• Introduction• Framework and Operation of CHIPS• Safety Effects• Diversion Effects • Driver Survey• Conclusion





Irvine

Background

ITS AWIS Central ControllerTraffic SensorsChangeable Message Signs

provide traffic information to travelers potentially:

-> increase safety-> improve the efficiency of traffic system

Benefits

work zones have become one of source of traffic congestion





Irvine

Background

Example of AWIS ADAPTIR CHIPS Smart Zone TIPS

Evaluation studies Most studies: system functionality and reliability Few studies: effectiveness of AWISs





Irvine

Objectives & approach

Evaluation of CHIPS Developed by ASTI Deployed in southern California

focus: effectiveness Safety effects Diversion effects Drivers’ acceptance

Approach: before and after study





Irvine

• Introduction• Framework and Operation of CHIPS

System Structure Study Area System Setup

• Safety Effects• Diversion Effects • Driver Survey• Conclusion

OUTLINE





Irvine

System Structure





Irvine

Study Area

Site Location City of Santa Clarita, 20 miles north

of Los Angeles, on freeway I-5 I-5: 4-lane freeway with the closure

of one lane on the median side Construction zone: 1.5 miles long Parallel route: the Old Road

System Configuration - 3 RTMSs - 5 PCMSs - 3 CCTV cameras





Irvine

System Setup

ScenarioQueue Detector CMS Combo Message

RTMS-1 RTMS-2 RTMS-3 PCMS-1 PCMS-2 PCMS-3 PCMS-4 PCMS-5

SBS01 F F F CMB01 CMB01 CMB01

SBS02 T F F CMB02 CMB03 CMB05

SBS03 T T F CMB06 CMB07 CMB03 CMB10

SBS04 T T T CMB06 CMB07 CMB08 CMB09 CMB11

T = Queue being detected, F = No queue being detected

Scenario SBS04: all three RTMSs have congestion, the following messages are shown on PCMSs:

CMB06 : SOUTH 5/TRAFFIC/JAMMED, AUTOS/USE NEXT/EXIT CMB07 : JAMMED/TO MAGIC/MOUNTAIN, EXPECT/10 MIN/DELAY CMB08 : JAMMED/TO MAGIC/MOUNTAIN, EXPECT/15 MIN/DELAY CMB09 : TRAFFIC JAMMED TO MAGIC MTN, AVOID DELAY USE NEXT EXIT CMB11: SOUTH 5 ALTERNAT ROUTE, AUTOS USE NEXT 2 EXITS





Irvine

• Introduction• Framework and Operation of CHIPS• Safety Effects

Data Collection Traffic Throughput Travel Speed

• Diversion Effects • Driver Survey• Conclusion

OUTLINE





Irvine

Data Collection

Collection locations RTMS-1: 0.15 mile before construction RTMS-2: 1.19 miles before construction

Collection time Before scenario : Aug. 17th, 2003 After scenario : Sep. 1st , 2003

Collection Methods Jamar DB-100 counters and Bushnell Speed Guns





Irvine

Traffic Volume Variance

Total Lane 1 Lane 2 Lane 3 Lane 4

RTMS-1 BeforeAfter

11.66.5

11.66.5

15.76.3

3.44.5

7.87.6

RTMS-2 BeforeAfter

37.431.2

4.44.2

2.84.6

3.94.3

1.82.4

11.66.5

15.76.3

44.925.4

Difference between before and after values is significant (90% confidence level)

With the grouped traffic data, the difference of variance was significant at RTMS-1, which means that the variance of the after scenario was statistically smaller than that of the before scenario With lane-based traffic data, the significant differences of variances were found for lane 1 and lane 2 at RTMS-1

Variance of traffic volume based on 1-min data





Irvine

Speed Mean and Variance

# of Samples

Sample Mean

Standard Deviation

Sample Variance

RTMS-1BeforeAfter

979970

29.930.6

8.97.1

80.050.2

RTMS-2BeforeAfter

1,186993

21.221.0

5.73.7

32.413.5

RTMS-1 RTMS-2

80.050.232.413.5

Difference between before and after values is significant (90% confidence level)





Irvine

• Introduction• Framework and Operation of CHIPS• Safety Effects• Diversion Effects

Data Collection Calculation of Diversion Diversion Estimation Travel Time Analysis

• Driver Survey• Conclusion

OUTLINE

Lake HughesOff-ramp

Hasley CanyonOff-ramp

SR-126

I-5Old Road

Rye CanyonOff-ramp

Magic MountainOn-ramp

ValenciaOn-ramp

Old Road I-5





Irvine

Data Collection

Collection Methods I-5 mainline traffic volume : PeMS database Off-ramp traffic volume : Tube counter

Collection Periods Before scenario : May 13th ~ May 18th,2003 May 18th

After scenario : Independence Holiday weekend (June 30th ~ July 7th, 2003) July 6th

Labor Holiday weekend (Aug. 30th ~ Sep. 2nd, 2003) Sep. 1st





Irvine

Calculation of Diversion

Proportion-based method

P = Voff

V

V

Voff

I-5 S

Old road

= Pa - Pb =Voff

a

VaVoff

b

Vb

Vd = Va

Proportion

Diversion rate

Diversion traffic volume

a : after scenariob : before scenario





Irvine

Diversion Estimation

Hasley Canyon off-ramp traffic proportions





Irvine

Diversion Estimation

Estimation of diversion traffic volume

Based on Caltran’s traffic report regarding Maximum DelayOn July 6th 15:30 ~ 17:30On Sep. 1st 17:30 ~ 20:00





Irvine

Travel Time Analysis

Comparison of travel times- July 6th ,2003 by GPS-based probe vehicles survey





Irvine

Driver Survey

Method : Postcard-based survey Location : Lake Hughes and Hasley Canyon off-

ramp Date : 1:40~4:30 PM, Sunday, July 6th , 2003 Response rate : 25% (100/400)





Irvine

Driver Survey

Did the traffic signs influence route choice? Yes : 78% of people who saw the PCMS message

Why did you get off the I-5 south? 73% : avoid traffic 22% : buy gas and foods 5% : arrived at destination

Did you find these signs useful? (check all that apply) 70% : useful for providing information 63% : useful for taking alternative routes 53% : useful for avoiding delay 48% : useful for reducing anxiety 9% : NOT useful





Irvine

Conclusion

Three aspects of effectiveness studies were conducted, including traffic diversion, safety effects, and responses from travelers

The results of these studies showed that: Obvious diversion were observed on two evaluation

dates, July 6th and September1st Based on the study of the effects of traffic flow, the

driving environment after the use of CHIPS seemed safer

Positive responses about the system were obtained based on driver surveys.





Irvine

Conclusion

• The safety has been enhanced– Stable traffic condition (speed and volume

variance)• Network performance improved

– 12% of diversion was observed– Alternative was still faster than mainline

• Driver response– 70% of drivers expressed the system to be useful

• Direct quantification was not made, but found positive effectiveness of the system.

Documents

Evaluation of Effectiveness of Automated Workzone Information Systems