Dallas Horseshoe ATM Design
Mike Holt, PE, PTOE
Senior ITS/Traffic
Engineering Manager
Project Background
 $798 million Design-Build project south of
Downtown Dallas
 Reconstruction of I-30/I-35E interchange and
approaches across Trinity River
 Construction of new signature bridge over I-30
 Started construction summer 2013; scheduled
completion fall 2017
Project Team
 Texas DOT is owner
 Pegasus Link Constructors is D-B Joint Venture
(Fluor Enterprises and Balfour Beatty Infrastructure)
 Parsons Brinckerhoff is lead design firm
Existing Conditions
 460,000 ADT through interchange
 I-30/35E “canyon” depressed freeway section
with 8 mainline lanes and auxiliary lanes
 Extensive existing signage
 Multiple lane closures and ramp detours
Existing Aerial Overview
Existing Conditions Photos
ATM Overview
 ATM proposed for value added project feature
ATM Overview
 Initial proposal included:
 Overhead lane control signals (LCS)
 Dynamic message signs
 Travel time signs
 Contractor negotiated DMS and TTS out of
project scope
 PB proceeded with LCS design
Lane Control Signals
 8 locations include:
 New overhead gantries (4)
 Existing bridge attachments (3)
 Existing overhead sign bridge attachment (1)
Lane Control Signals
 Skyline SlimLine LED Variable Message Signs
 5’ x 5’ full color matrix
 64 x 064 pixel layout
 336S cabinet
 2070 ATC controller
 Envoy DMS Central Control Software
Design Challenges
 Power
 Communications
 Structural attachments
 Sign visibility
Power
 120/240 VAC
 50 amp service to cabinet
 20 amp service to each LCS
 Alpha Micro Secure 100 UPS
Power Challenges
 Need meter and disconnect for some cabinets
 Use existing ITS service for some cabinets
 Service points were not always close to LCS
 Prepared voltage drop calculations for service
conductor sizing
Communications
 Wireless communications to temp. project TMC
 Sierra Wireless AirLink LS300 Gateway
 AntennaPlus Hockey Puck antenna
 Cat 5e cabling from cabinet to LCS
Communications Challenges
 Existing fiber network not accessible
 Cellular comm. to temporary TMC
 Cat 5e cabling limitations (<300’)
Communications Schematic
Structural Attachments
 Gantry
 Existing bridge
 Existing OH sign bridge
 Submitted customized structural details
Structural Details
Structural Details
Structural Details
Sign Visibility
 Reviewed available guidance documents for LCS
visibility requirements:
MUTCD Section 2L.03
Legibility and Visibility of Changeable Message Signs

Offers guidance that CMS on roadways with speed limits of 55
mph or higher that messages should be legible from a
minimum distance of 600 feet for nighttime conditions and 800
feet for normal daylight conditions.
Sign Visibility
MUTCD Section 4D.12
Visibility, Aiming and Shielding of Signal Faces

Offers guidance that traffic signal faces should be continuously
visible to approaching traffic, from a point at least the minimum
sight distance provided in Table 4D-2
85th-Percentile Speed
20 mph
25 mph
30 mph
35 mph
40 mph
45 mph
50 mph
55 mph
Minimum Sight Distance
175 feet
215 feet
270 feet
325 feet
390 feet
460 feet
540 feet
625 feet
Sign Visibility
MUTCD Section 4M.03
Design of Lane-Use Control Signals

States the color of lane-use control signal installations shall be
clearly visible for 2,300 feet at all times, unless otherwise
physically obstructed
Sign Visibility
 Analysis
 Section 2L.03 applies to CMS (messages vs. LCS)
 Section 4D.12 addresses traffic signals (single color)
 Section 4M.03 most commonly applied to reversible-
lane control and toll plaza lanes (more complex)
Section 4D.12 (625’) appears most appropriate for LCS
visibility
LCS Deployment
 Recommendations
 LCS #1 (I-30 EB) – proposed gantry
 LCS #2 (I-30 EB) – proposed gantry
 LCS #3 (I-30 WB) – existing bridge
 LCS #4 (I-30 WB) – existing bridge
 LCS #5 (I-35E NB) – proposed gantry
 LCS #6 (I-35E NB) – existing bridge
 LCS #7 (I-35E SB) – existing OH sign structure
 LCS #8 (I-35E SB) – proposed gantry
Gantry Plan
Bridge Mount Plan
OSB Mount Plan
LCS Deployment
LCS Deployment
LCS Deployment
LCS Deployment
LCS
Mounting
Current Progress
Current Progress