HISTORY. 1980s. Three strand guard cable used with great success on I-270 around St. Louis.

Transcription

1

2 HISTORY 1980s Three strand guard cable used with great success on I-270 around St. Louis.

3 HISTORY

4 HISTORY 1980s Three strand guard cable used with great success on I-270 around St. Louis. Very successful installation that met with critical acclaim Eventually removed because narrow median was replaced with additional lanes and concrete barrier.

5 HISTORY 1990s Three strand guard cable installed on I-44 west of metro St. Louis.

6 HISTORY

7 HISTORY 1990s Three strand guard cable installed on I-44 west of metro St. Louis. Used to address several spot concerns With standards still being developed nationwide, cable was placed on slopes much steeper than 6:1 and used for pier treatment

8 HISTORY

9 HISTORY 1990s Three strand guard cable installed on I-44 west of metro St. Louis. Used to address several spot concerns With standards still being developed nationwide, cable was placed on slopes much steeper than 6:1 and used for pier treatment Installation functioned well and remains very effective today

10 HISTORY 2000s Three strand guard cable installed on I-435 locations in Kansas City

11 HISTORY

12 HISTORY 2000s Three strand guard cable installed on I-435 locations in Kansas City Cable use caught on for sporadic use in outstate areas All installations functioned well and most met with great press In most cases, the maintenance problem has gone away because of contract maintenance

13 HISTORY Today Statewide program to minimize crossmedian crashes on all interstate highways with medians less than 60 ft. Funded with Section 154 Open Container Transfer Funds. Began in miles of guard cable have been installed to date. More than 300 additional miles of cable barrier being installed this year.

14 LESSONS LEARNED Maintenance Problem: Districts were hesitant to use cable barrier given it s high maintenance nature Solution: Maintenance is outsourced through ongoing contracts Solution: Newer generation (hightension) systems require less maintenance

15 LESSONS LEARNED Steep Slopes Problem: FHWA will not grant design exception for slopes steeper than 6:1 Solution: Grade median inslopes to 6:1 (discouraged) Solution: Use a double run of barrier to enclose median (preferred over grading) Solution: Use Brifen system, recently approved for 4:1 installations median (preferred over double run)

16 LESSONS LEARNED Guardrail Interface Problem: Guard cable interfaces single-sided guardrail well, but doesn t connect to bullnose Solution: Terminate barrier 25 ft. from bullnose. The separation keeps the two systems functioning as designed without any eccentricities introduced into the vehicle trajectory.

17 LESSONS LEARNED Length of Need (LON) Problem: The guardrail LON at many bridge ends is non-standard. Some designers believe it must be brought up to standard before cable barrier can be attached Solution: As an NCHRP 350 TL-3 approved barrier, guard cable will substitute as guardrail LON. The FHWA is in agreement.

18 LESSONS LEARNED Lateral Placement Problem: Missouri guard cable had traditionally been placed in the centerline of the median. Recently, this practice was believed to have the potential for failure. Solution: Consult with FHWA and AASHTO to discern latest information Solution: No installations in defined barrier not recommended areas

19 SINGLE RUN LOCATIONS PARALLELL RUN LOCATION FLAT BOTTOMED DITCH LOCATIONS SINGLE RUN LOCATION CL 10 2 RECOMMENDED LOCATIONS BARRIER NOT RECOMMENDED V-DITCH LOCATIONS PARALLELL RUN LOCATION CL

20 Education LESSONS LEARNED Problem: The concept of cable barrier is relatively new to most designers. There is also a lack of guidance in Missouri as well as nationwide. Solution: Maintain open dialogue with roadside safety expert at Central Office Solution: Publishing Technical Bulletin to educate designers in a straightforward manner

21 LESSONS LEARNED

22 Success Rate SUCCESS STORIES Recent data on in-service performance suggests that of every 100 cars that entered the median 94 were kept from entering the oncoming lanes.

23 SUCCESS STORIES Exceeding Expectations I-70, Mongomery County

24 Good Press SUCCESS STORIES

25 THE FUTURE High Tension Systems MoDOT will likely be using high-tension installations exclusively Advantage: Lower deflections Advantage: Less maintenance effort Advantage: Residual safety value Prices are coming down due to increased competition in the market

26 THE FUTURE In-Service Performance MoDOT is conducting a comprehensive evaluation of in-service performance for all current installations Data ranging from vehicle type and median width to inslope grade and weather will be recorded Final report will be used to refine future installations, assist with nationwide research, and provide more accurate benefit-cost calculations