Cable Barriers: Texas Research. Scott Cooner, P.E. Program Manager Texas Transportation Institute Arlington Office

Transcription

1 Cable Barriers: Texas Research Scott Cooner, P.E. Program Manager Texas Transportation Institute Arlington Office

2 Presentation Outline Cross-median crash problem Evolution of cable barrier in Texas Overview current research project Highlight key issues Wrap-up 2

3 Cable Barrier - Advantages Lower initial cost Effective vehicle containment Designed to facilitate quick and easy repairs Used with median cross slopes as steep as 4:1 Low deceleration forces upon the vehicle and its occupants No drainage issues 3

4 Cable Barrier - Challenges Accommodate deflection distance Damage even with moderate impacts Require maintenance every impact May require periodic inspections Containment of trucks Barrier penetration 4

5 Cross-Median Crashes: Urban 5

6 Cross-Median Crashes: Rural I-35 Hewitt 7 fatalities US75 Sherman 10 fatalities 6

7 Cross-Median Crashes: Stats 7

8 Median Barrier Warrants 30 feet 8

9 Traditional Median Barriers Jersey Single Slope 9

10 Cable Evolution in Texas Research support Project B/C >

11 Cable Evolution in Texas Safety bond $$$ million $157 million for cable median barrier 94 projects 738 miles $30 million Both CTB and cable 85 miles 17 of 25 Districts 11

12 Cable Evolution in Texas Cost, availability and experience Gibraltar Brifen Trinity NUCOR/GSI 12

13 Cable Evolution in Texas I-820 Fort Worth Summer mile Brifen 13

14 5609 Research Cable in-service performance evaluation Maintenance Safety Comparison of cable vs. concrete 18-month project Completion in February 2008 Interim CTB Permanent CTB Semi-Permanent CTB 14

15 5609 Research In-Service Evaluation of Cable Median Barrier Performance Program Coordinator A. Rory Meza (DES) Project Director Roy Parikh (FTW) Project Advisors Jimmy Bodiford (FTW) Brian Crawford (ABL) Bobby Dye (DES) Darwin Myers (DAL) Grover Schretter (FTW) Lance Simmons (ATL) 15

16 5609 Research: GIS Analysis Note: red line = cable barrier and black line = concrete barrier 16

17 Key Issues Design Placement Test level Post type Anchor Maintenance Impacts Repair Safety 17

18 Design: Placement TxDOT Design Division memorandum dated June 21,

19 Design: Placement TxDOT Design Division memorandum dated June 21,

20 Design: Placement Shoulder Higher frequency of impacts Maintenance concerns Median Both sides US75 Collin County

21 Design: Placement Provision of emergency crossovers Enforcement Response time Utilize overpass locations 21

22 Design: Test Level NCHRP 350 TL-3 TL-4 Primary consideration is truck percentage 22

23 Design: Post Type Socketed Mow Strip 23

24 Key Issue: Anchor Design Soil conditions Weather concerns I-20 Kaufman County 24

25 Maintenance: Impacts 25

26 Maintenance: Impacts I-20/I-30 Parker County TxDOT Fort Worth District 26

27 Maintenance: Impacts Barrier # of Impacts Avg. Posts Avg. Men Avg. Time (hrs) Volume Range Brifen K Trinity K NUCOR K TOTALS K 1 Brifen & Trinity data for 57 week time period 2 NUCOR data for 27 week time period 3 25 mile section on I-20/II 20/I-30 in Parker County 27

28 Maintenance: Impacts 28

29 Maintenance: $ Recovery High % unknown vehicles North Carolina State police damage tags Significant improvement 29

30 Maintenance: Impacts San Antonio 30

31 Maintenance: Impacts District San Antonio Roadway # of Miles 19 Barrier Type NUCOR/GSI Dates August 2006 April 2007 Total Average # of Impacts /month Linear Damage (ft) 11, # of Posts

32 Maintenance: Mileage Total Miles of Different Types of Cable Barrier System Installed in Texas 79 (25%) 15 (5%) Brifen CASS Nucor Gibraltar 42 (13%) 177 (57%) 32

33 Maintenance: Repair Level of Difficulty in Repairing the Cable Barrier System 1 (6%) 1 (6%) 3 (17%) 7 (38%) Easy Average Difficulty Somewhat Difficult Very Difficult No Answer 6 (33%) 33

34 Maintenance: Repair Availability of Repair Parts 5 0 (0%) 0 (0%) 4 (22%) (28%) Always Available Average Availability Somewhat Difficult Very Difficult No Answer 9 (50%) 34

35 Maintenance: Repair Average Time Spent on Repairs 3 (18%) 2 (12%) 1 (6%) 3 (18%) 8 (46%) 0-1/2 Hour > 1/2 Hour > 1 Hour > 2 Hours > 3 Hours 35

36 Maintenance: Containment Number of Maintenance Sections with Penetration of Passenger Vehicles through the Cable Median Barrier System 4 (22%) Yes No 14 (78%) 36

37 Maintenance: Containment Number of Maintenance Sections with Penetration of Trucks through the Cable Median Barrier System 5 (28%) Yes No 13 (72%) 37

38 Maintenance: Mow Strips Number of Maintenance Sections with Mow Strips along the Cable Barrier System Installation 6 (33%) Yes No 12 (67%) 38

39 Safety: Fatal Crashes One year before and after mi. of cable One-year Pre-Installation One-year Post-Installation Cross-Median Cross-Median Cross-Median Cross-Median Fatal Crashes Fatalities Fatal Crashes Fatalities

40 Wrap-up: Website Homepage 40

41 Wrap-up: In-Service Assistance Cable Barrier Maintenance/Repair Log Form Page 41

42 Wrap-up: Conclusions Texas is aggressively installing cable median barriers Preliminary results are positive For more information: Project median barrier guidelines report: Contact me: (817) or 42