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Section 5: Operational Design

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Overview

Operational design involves subsections of Illumination, Intelligent Transportation Systems, Signals, and Signing/Striping. Construction plans result from each of the tasks within this section. This section includes the following groups of tasks. The tasks may be performed concurrently.

50500. Design illumination

50510. Design Intelligent Transportation System

50520. Design signalization plan

50530. Design signing and pavement markings

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Illumination

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50500: Design illumination

Description. There are two types of roadway lighting: continuous lighting that meets warrants and safety lighting.

Safety lighting is typically needed at interchanges, decision points, high-volume rural or suburban intersections, weigh stations, rest areas, and safety/security for pedestrians, bicyclists and transit users.

Continuous lighting provides uniform lighting on all mainlanes, ramps, direct connectors, and interchanges. Continuous lighting requires the financial participation of the city. Either type may use conventional roadway lighting or high mast poles.

Determination of the eligibility of the project for illumination and compliance with warranting conditions should have been initiated when preliminary illumination locations were established in Task 20580: Establish preliminary illumination locations.

An FAA form 7460-1 must be completed according to 14 CFR §77.9. Required notification applies to any construction or alteration:

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  • Exceeding 200 feet above ground level (AGL)
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  • Within 20,000 feet to a public use or military airport, which exceeds 100:1 surface from any point on the runway of each airport with its longest runaway more than 3,200 feet
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  • Within 10,000 feet to a public use or military airport, which exceeds 50:1 surface from any point on the runway of each airport with its longest runway no more than 3,200 feet
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  • Within 5,000 feet of a public use heliport, which exceeds a 25:1 surface

Pertinent Project Types. Projects warranting continuous roadway lighting or safety lighting

Responsible Party. Designer with illumination experience

Subtasks.

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  • Obtain agreement with local government for maintenance of proposed continuous lighting.
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  • Obtain preliminary roadway, drainage, traffic, and utility adjustment plans.
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  • Obtain design year traffic data.
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  • Make a site visit to inspect existing conditions. Lighting design needs to coordinate with roadway features, maintenance and operations issues, and surrounds.
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  • Obtain or prepare a lighting justification report.
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  • Design high mast foundations according to bore logs and HMIF standard sheets.
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  • Coordinate plans with roadway design, traffic, and structural engineers.

Helpful Suggestions.

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  • Technical assistance with design is available from the Traffic Operations Division - Traffic Engineering Section (TRF-TE).
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  • Use breakaway devices according to TxDOT Highway Illumination Manual and AASHTO requirements.
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  • Find out where traffic barrier will be located. Try to place illumination structures behind barrier or protect with barriers designed for light pole structures.
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  • Determine the locations of existing and proposed utilities, drainage facilities, and traffic signs and signals.
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  • Consider maintenance requirements when locating illumination supports.
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  • For lighting on bridges, coordinate design illumination with bridge details so conduit is made part of bridge plans; this will avoid unsightly conduit additions to bridges.
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  • Determine illuminance design values according to roadway classification and AASHTO Roadway Lighting Design Guide.
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  • Texas is required by statute to use cutoff luminaires to minimize glare and light pollution when installing lighting using state funds.
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  • When designing lighting for a walkway adjacent to a roadway, the street must be lit to the same level as the walkway.

Authority.

Resource Material.

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Intelligent Transportation System

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50510: Design Intelligent Transportation System (ITS)

Description. ITS projects should be designed in accordance with the National ITS Architecture. The ITS system aims to solve congestion and safety problems and improve operating efficiency in freight and transit movement.

ITS applications include the following:

The project manager should coordinate work with the district traffic engineer, the Traffic Operations Division - ITS and Signal & Radio Operations Branches and the Information Management Division (IMD) to ensure compliance with IT core architecture and other TxDOT requirements.

The department maintains a statewide radio network providing signal and radio technical support and coordinating radio frequency licenses. The Highway Advisory Radio Stations (HARS) are low power AM stations that broadcast highway related information to the traveling public. FCC regulations require that traveler information stations transmit only noncommercial voice information pertaining to traffic and road conditions.

By Executive Order, June 14, 2012, federal-aid highways and rights of way can be used to deploy both wired and wireless broadband infrastructure creating funding opportunities for State and local transportation infrastructure to help expand broadband infrastructure. Broadband access also affords public safety agencies better interoperability and effectiveness.

Pertinent Project Types. Projects involving high traffic volumes or complex traffic movements; however, rural projects with lower traffic volumes may need ITS applications.

Responsible Party. Project manager, traffic operations engineer

Subtasks.

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  • Find out where traffic barrier will be located, and try to place hazardous objects behind barriers that are already proposed for other purposes.
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  • Obtain recent information on ITS alternatives, this is a rapidly advancing field.
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  • Incorporate standard communications equipment when possible.
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  • Consult with the District Traffic Engineer and the ITS or Signal & Radio Operations Branches of the Traffic Operations Division.
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  • When possible, submit plans to Traffic Operations Division for early review.

Helpful Suggestions.

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  • Technical assistance is available from TRF Division for designing ITS and developing contracts for ITS design or construction.
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  • Consider future maintenance requirements for the system. Design to minimize maintenance, but also consider how maintenance will be performed safely with minimum impact on traffic.
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  • Consider placement of DMS in areas where there is not a high probability of a simultaneous workload required for drivers (i.e. high-decision locations, high-speed merging, weaving).
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  • Consider ITS regional opportunities and possible connections to manage traffic through long corridors.
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  • Utilize existing structures and roadside barriers for ITS, if possible.

Critical Sequencing.

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  • ITS plans should be designed concurrently with roadway plans to assure that necessary provisions, such as mounting structures and conduit systems, are made part of the overall plans.

Authority.

Resource Material.

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Signals

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50520: Design signalization plan

Description. A comprehensive investigation of traffic conditions and characteristics of potential signal locations is necessary to determine the need for signal installations and to collect data for the design and operation of signals.

Traffic control signals should not be installed, unless the investigation reveals that at least one of the warrants contained in the Texas Manual on Uniform Traffic Control Devices (TMUTCD) is met. Meeting an hourly volume warrant is only the first step to justifying a traffic signal. The TMUTCD states that warrants are a threshold condition and not a substitute for engineering judgment. All traffic factors should be considered when determining if a signal(s) should be installed.

Signal operation types include full-actuated, semi-actuated, pre-timed, or combinations thereof. They can also be operated at isolated intersections, in coordination with nearby signals, or as mid-block operations.

If the department is not responsible for the traffic control signal system operation and maintenance (appurtenances, software, hardware, and timing), then an agreement should be established with the controlling agency before the signal is installed and activated.

Pertinent Project Types. Projects warranting signalization

Responsible Party. Traffic engineer

Subtasks.

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  • Obtain or perform a signal warrant study.
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  • A roadway design engineer may design the signals and prepare the plans; however, a traffic or transportation engineer should carefully check the design and specifications.
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  • Coordinate plans with the roadway design engineer, drainage engineer, etc.
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  • Coordinate signal design and details with local government, if signals will be operated and maintained by a local government.
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  • Obtain concurrence from the local government for locating signals within their jurisdiction and ensure that required agreements are executed as described in the TxDOT Negotiated Contracts Procedures Manual, Traffic Engineering Agreements.
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  • Obtain preliminary roadway, drainage, and utility adjustment plans.
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  • Obtain existing and design year traffic data.
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  • Make a site visit to inspect existing conditions and verify intersection and stopping sight distances.
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  • Order and obtain geotechnical foundation designs for signal foundations.

Helpful Suggestions.

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  • Technical assistance is available from the district traffic engineer and the Traffic Operations Division - Traffic Engineering Section.
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  • Coordinate intersection geometry, turn lane lengths, median types, and access control at signalized intersections. In urban areas having remote signal timing control and coordinated signals, signal control design should be discussed with the local entity.
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  • Signal and supports should be located to maximize safety and meet PROWAG and TAS accessibility requirements. All pedestrian features and pedestrian signal poles must be accessible to persons with disabilities.
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  • Detail intersection striping, ramps, and walkways before preparing pedestrian signal layouts to ensure proper location of pedestrian poles and signal heads.
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  • Pedestrian crossing times should be sufficient for the expected user population to cross the street safely, and meet or exceed the requirements contained in the TMUTCD.

Resource Material.

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Signing and Striping

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50530: Design signing and pavement markings

Description. Signing and pavement marking plans include plan view layouts of final signs, striping, pavement markers, and other pavement markings. Show cross sections and sign size and legend details for the locations of all overhead signs. Detail all ground mounted guide signs and reference locations on the plans. Use sign summary sheets to detail color, location, size of structural steel.

Pertinent Project Types. All projects

Responsible Party. Traffic engineer

Subtasks.

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  • Obtain roadway and drainage plans.
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  • Prepare a signing, striping, and pavement marking schematic and obtain preliminary approval from the Traffic Operations Division for roadways with new guide signing. This is not required for upgrades of existing signs; in this case, plans can be prepared without schematics.
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  • Obtain a geotechnical survey and coordinate with a structural engineer when designing overhead sign bridge foundations.
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  • Coordinate plans with the roadway design engineer.
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  • Prepare final signing and pavement marking plans.

Helpful Suggestions.

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  • Consider contrast and shadow markings on light-colored pavements.
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  • If a fixed-site Commercial Motor Vehicle (CMV) inspection facility is within the project limits, confirm if signing meets the Traffic Division Standard sheets for freeway CMV inspection stations. Coordinate with Texas Department of Public Safety. See Task 20540: Perform preliminary planning for commercial motor vehicle inspection stations.
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  • Roadway and traffic engineers should coordinate intersection and ramp geometry early in the design process. There may be some areas of channelization improvement that become apparent only when preliminary striping designs are prepared.
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  • Roadway and traffic engineers need to coordinate lane transitions at project ends (especially lane drops) during early stages of design. The combination of signing and design speed requirements will likely require the lane transition to be longer than geometrically necessary.
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  • Overhead sign bridge supports should be located to maximize safety.
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  • Striping of pedestrian facilities, such as crosswalks, must be closely coordinated with the design of curb ramps.

Critical Sequencing.

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  • Preliminary design can be as simple as a line diagram showing proposed number of lanes, lane drops, and proposed overhead and large ground mounted, guide signs, and their proposed locations.

Resource Material.
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