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Evaluation of LED-Outlined Backplates at Intersections With Light Rail Lines In Houston, Texas ITS Texas Annual Meeting, November 2014 Jonathan Tydlacka, P.E. (TTI)
Evaluation of LED-Outlined Backplates at Intersections With Light Rail Lines
In Houston, Texas
ITS Texas Annual Meeting, November 2014 Jonathan Tydlacka, P.E. (TTI)
Why Are We Here Today? • Great forum to present results of
evaluations of innovative traffic control devices
• Seek feedback and comments on the operational concepts
METRORail History
• METRORail Red Line opened in Houston, Texas - January 2004
• Extended North - January 2014 • Completely at-grade with shared
left turn lanes in some areas • Line operates from North Loop,
CBD, down to Texas Medical Center, and Reliant Park
• Currently carries about 42,000 passengers per day
Initial Operational Issues
• High Frequency of Accidents (15) in 6 weeks of testing & 1st month of revenue operation
• All with motor vehicles
• All were low speed collisions at intersections
• Collisions were sudden from LRV perspective
• All attributed to motorist error
TCD Experimentation
• Stop bar location & visibility – Lighted Stop Bar
• Increase visibility of red signal indications – LED-outlined Backplates
Evaluation Methodology
• TCD Experimentation Request • Driver Surveys • Operational Evaluations
– Before / After – Measures of Effectiveness (violations)
• Long Term Crash Monitoring – Crashes by type/causation
• Semi-annual reports
Lighted Stop Bar Pilot Installation
• EB Jefferson Street at Main Street • FHWA Approved Experiment 4-295-EX • Stop Bar activated March 25, 2006 • Operational Aspects as Initially Evaluated:
– Markers operated in a steady red mode during every red signal indication of the traffic signal
– Markers off at all other times – Markers located prior to painted stop line
Pilot Installation
Replacement System & Additional Locations • Several failures at pilot installation • Pilot site & additional sites outfitted to 3G & 4G system
• FHWA granted request to expand experimentation
Lighted Stop Bar Problems
• Newer 3G and 4G systems had durability issues
• Failures of the individual markers and the systems
• High traffic volumes, moisture, debris penetration – all factors leading to failure.
• Systems had IP addressable markers, so failures were reported BUT…
• The costs for repairs and replacements were too great in terms of dollars and manpower – A change was necessary.
LED-Outlined Traffic Signal Backplates
• Around the same time that the first pilot lighted stop bar was being tested, METRO was also testing a pilot location of LED-outlined traffic signal backplates
• The backplates were part of the same FHWA Experimentation Request.
LED-Outlined Backplates Pilot Installation
• WB Gray at Main Street • FHWA Approved Experiment 4-295-EX • Backplates activated October 13, 2006 • Operational Aspects:
– Red LEDs create a red border around the standard black traffic signal backplate for each signal head on the approach.
– Operate in a steady red mode during every red signal indication of the traffic signal & Off at all other times (including red or yellow flash).
LED-Outlined Backplates
• Mounted to signal mast arm
• Two signal faces
• No backplates before LED-outlined backplates added
LED-Outlined Backplates
LED-Outlined Backplates Results Motorist Violation Data – Pilot Site
Evaluation Period
24-hour Totals of WB Vehicles
WB Violations per Day
WB Violations per Day per
10,000 Vehicles
Left Turn Thru Right
Turn RLR* RTOR* RLR RTOR
Before (3 Day Average) 401 8089 381 19 68 22 76
After (3 Day Average) 273 6870 351 8 53 11 71
*RLR = Red Light Running *RTOR = Right Turn on Red Note: RTOR prohibited on all cross street approaches to the Red Line
LED Backplate - Vehicle Crash Statistics
• Crash statistics compiled for 24 months before and after the installation of the LED Backplates.
Period Total Crashes Ran Red Light (WB)
Before 24 Months 3 2
After 24 Months 1 0
Maintenance & Durability Comparisons
Issue LED-Outlined Backplates Lighted Stop Bar
Installation
•Attach to signal pole or mast arm •No Experience with Span Wire
•Saw Cut, Run Cables •Anchor Markers •Time-consuming
Maintenance •None •Replace markers if full or partial failure
Durability
•Works fine for years (8+ years and counting) •Only failure - over-height truck
•Marker failure due to wheel impacts (very common) •System/wiring failures (less common)
Replacement •Purchase new LED strip •Assemble & Install
•Vendor/contractor remove old marker & drop in new one
Monetary Cost Comparisons
Issue LED-Outlined Backplates Lighted Stop Bar
Initial Capital Cost (One Typical Approach)
•$2,500 - $3,000 each •$5,000 - $6,000 per 2 signal intersection
•$70,000 (about 30 markers)
Ongoing Maintenance Costs •None
•If no warranty (likely), then $20,000 per approach per year
Observational Study of Additional Sites • Three LED-outlined backplate treatment
sites for Before & After Study – Westbound Pease at Main – Westbound Bell at Main – Westbound Franklin at Main
• Pease & Bell are five-lane, one-way approaches to the Red Line, Franklin is a three-lane approach.
• Replaced standard backplates with LED-outlined backplates
Observational Study of Additional Sites
• Before & After Study using recorded video
– 3 days (three 24-hour periods) of video before – 3 days of video after backplates installed and
activated • Approx 5-8 weeks after activation
– Manually reduced video
• Study still ongoing – Data is complete for Pease at Main treatment location
Observational Study of Additional Sites
• Several differences from pilot location
• Mounted to signal poles (one on each side)
• Two signal faces
• Pease site had backplates before LED-outlined backplates added
Observational Study of Additional Sites • Data included traffic volumes and violations
– Red Light Running (RLR) – Right Turn On Red (RTOR)
• RTOR prohibited on all cross street approaches to the Red Line
• Some deliberate RLR violations in both
before and after periods – Violations occuring after more than 90 seconds
of red time were removed
Three Day Average Violation Frequency
24-hour Totals of WB
Vehicles WB Violations
per Day
WB Violations per Day Day*
(Daylight) Night
(No Daylight) Left Turn Thru Right
Turn RLR RTOR RLR RTOR RLR RTOR
Before (3 Day
Average) 106 10794 223 10.33 24.33 7.67 20.33 2.67 3.67
After (3 Day
Average) 84 10115 176 8.67 19.33 7.00 15.33 1.67 4.00
% Change -21% -6% -21% -16% -21% -9% -25% -37% +9%
*Note: Day includes daylight and twilight periods of the day.
Westbound Pease at Main – Treatment Site
Notes on Violation Frequency • Reduction of RLR and RTOR at each
treatment site – Similar reductions for both day and night, except for
RTOR at night, which essentially stayed the same
• Normalized data to account for different approach traffic volumes – Violations per 10,000 cross street approach vehicles – Pooled t-Test used to determine significant
differences in Before vs. After data
Normalized Violation Data
Study Site Study Period
3-Day Average Number of Violations per Day per
10,000 Vehicles
Statistically Significant Reduction in Violations per Day per 10,000 Vehicles?
RLR RTOR RLR RTOR
Pease at Main
Before 9.3 21.9
NO
YES
90% Confidence
Level After 8.4 18.6
Additional Observational Study Data • Time of violation after onset of red signal
(> 2) Signal red more than 2 seconds (≤ 2) Signal red less than or equal to 2 seconds
– RLR
• More RLR in ≤ 2 data • Reduction of 20% for > 2 • Reduction of 15% for ≤ 2
Crash Monitoring
• Long-term crash analysis still ongoing for these and all LED-outlined backplate locations
• Being done to provide additional data points at FHWA & TxDOT request
In Summary • LED-outlined backplates show potential to supplement the
effectiveness of standard TCD’s along the LRT – Reduction in red light running – Reduction in illegal right turn on red movements
• Helped to reduce RLR and RTOR violations at the treatment site.
Discussion • Results slightly different for this recent treatment due to
some changes in installation characteristics as well as other factors.
• Previously saw greater reduction of RLR when comparing LED backplates to no backplates. Now, our “before” data had “regular” backplates.
• Previously, LED backplates were mounted on a signal mast arm, visible over the lanes. That seems to have made a greater positive impact than mounting them on signal poles.
• Two other sites currently being analyzed – these will add even more understanding and confidence to the evaluation.
METRO’s View On Experimental TCD’s • Working with its local, state and federal
partners, METRO plans to continue developing and deploying innovative TCD’s where in the best interest of its passengers and the traveling public.
• METRO plans to use the LED-outlined backplates on new light rail lines currently under design and initial stages of construction.
METRO’s View On Experimental TCD’s • METRO is seeking to garner support for interim
approval to use these devices within its jurisdiction.
• NCUTCD (National Committee) will be making decisions soon about what is included in next MUTCD
• METRO has demonstrated these TCDs to visiting agencies, and conveyed the success of the devices among peers (i.e., APTA Conference in Houston this year)
For More Information • TTI
– Jonathan Tydlacka, P.E. • [email protected]
– 713-686-2971
• Houston METRO – Walter Langford, III
• [email protected] – 713-652-4377
Driver Survey Results • LED Backplate
– The focus group tested a flashing LED-outlined backplate concept with both yellow and red indications
– This operation was later changed to steady red only in the field.
– 95% recognized the LED-outlined backplates – 75% responded that the purpose was to draw attention
to the yellow and red signals.
– There was no indication from observation of video of field deployment that drivers are misinterpreting the steady red LED backplate.
