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1 Evaluation of Effectiveness of Automated Workzone Information Systems Lianyu Chu CCIT, University of California Berkeley Hee-Kyung Kim, Yonshik Chung, Will Recker University of California Irvine
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2 OUTLINE Introduction Framework and Operation of CHIPS Safety Effects Diversion Effects Driver Survey Conclusion
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3 Background ITS AWIS Central Controller Traffic Sensors Changeable 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
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4 Background Example of AWIS ADAPTIR CHIPS Smart Zone TIPS Evaluation studies Most studies: system functionality and reliability Few studies: effectiveness of AWISs
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5 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
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6 Introduction Framework and Operation of CHIPS System Structure Study Area System Setup Safety Effects Diversion Effects Driver Survey Conclusion OUTLINE
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7 System Structure
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8 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
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9 System Setup Scenario Queue DetectorCMS Combo Message RTMS-1RTMS-2RTMS-3PCMS-1PCMS-2PCMS-3PCMS-4 PCMS-5 SBS01FFFCMB01 SBS02TFFCMB02CMB03CMB05 SBS03TTFCMB06CMB07CMB03CMB10 SBS04TTTCMB06CMB07CMB08CMB09CMB11 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
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10 Introduction Framework and Operation of CHIPS Safety Effects Data Collection Traffic Throughput Travel Speed Diversion Effects Driver Survey Conclusion OUTLINE
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11 Data Collection Collection locations RTMS-1: 0.15 mile before construction RTMS-2: 1.19 miles before construction Collection time Before scenario : Aug. 17 th, 2003 After scenario : Sep. 1 st, 2003 Collection Methods Jamar DB-100 counters and Bushnell Speed Guns
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12 Traffic Volume Variance TotalLane 1Lane 2Lane 3Lane 4 RTMS-1 Before After 11.6 6.5 11.6 6.5 15.7 6.3 3.4 4.5 7.8 7.6 RTMS-2 Before After 37.4 31.2 4.4 4.2 2.8 4.6 3.9 4.3 1.8 2.4 11.6 6.5 15.7 6.3 44.9 25.4 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
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13 Speed Mean and Variance # of Samples Sample Mean Standard Deviation Sample Variance RTMS-1 Before After 979 970 29.9 30.6 8.9 7.1 80.0 50.2 RTMS-2 Before After 1,186 993 21.2 21.0 5.7 3.7 32.4 13.5 RTMS-1RTMS-2 80.0 50.2 32.4 13.5 Difference between before and after values is significant (90% confidence level)
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14 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 Hughes Off-ramp Hasley Canyon Off-ramp SR-126 I-5 Old Road Rye Canyon Off-ramp Magic Mountain On-ramp Valencia On-ramp Old Road I-5
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15 Data Collection Collection Methods I-5 mainline traffic volume : PeMS database Off-ramp traffic volume : Tube counter Collection Periods Before scenario : May 13 th ~ May 18 th,2003 May 18 th After scenario : Independence Holiday weekend (June 30 th ~ July 7 th, 2003) July 6 th Labor Holiday weekend (Aug. 30 th ~ Sep. 2 nd, 2003) Sep. 1 st
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16 Calculation of Diversion Proportion-based method P = V off V V I-5 S Old road = P a - P b = V off a VaVa V off b VbVb V d = V a Proportion Diversion rate Diversion traffic volume a : after scenario b : before scenario
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17 Diversion Estimation Hasley Canyon off-ramp traffic proportions
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18 Diversion Estimation Estimation of diversion traffic volume Based on Caltran’s traffic report regarding Maximum Delay On July 6 th 15:30 ~ 17:30 On Sep. 1 st 17:30 ~ 20:00
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19 Travel Time Analysis Comparison of travel times - July 6 th,2003 by GPS-based probe vehicles survey
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20 Driver Survey Method : Postcard-based survey Location : Lake Hughes and Hasley Canyon off-ramp Date : 1:40~4:30 PM, Sunday, July 6 th, 2003 Response rate : 25% (100/400)
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21 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
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22 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 6 th and September1 st 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.
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23 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.
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