4.4.8 Traffic Design

4.4.8.1 Large Guide Signs
Large guide signs direct road users along streets and highways and are shown on the geometric schematic. Large guide signs show route designations, destinations, directions, distances, services, points of interest, and other geographical, recreational or cultural information.
Freeways and expressways use large guide signs that exceed the requirements and specifications for conventional roads. These include advance guide signs for interchange exits, supplemental signs, exit direction signs, diagrammatic signs and several other miscellaneous sign types. Refer to the TMUTCD for more information on guide signs for freeways and expressways.
Existing guide signs should be evaluated to determine if they are still applicable for the project. Based on traffic and crash data, the designer should determine the guide signs needed to increase roadway operational efficiency and safety and these signs are shown on the geometric schematic.
4.4.8.2 Preliminary Illumination Locations
Preliminary illumination locations should be developed and shown on the geometric schematic. Illumination infrastructure must meet the requirements of the American Association of Highway and Transportation Official’s (AASHTO)
Roadway Lighting Design Guide
 and the TxDOT standard equipment and spacing as detailed in the standard specifications and the
Highway Illumination Manual
.
Electrical systems must be designed in accordance with the
National Electrical Code
. A preliminary illumination layout must be prepared showing pole locations and power sources. Also provide a layout showing the photometry and foot-candle reading.
Federal Aviation Administration (FAA) requires notification of construction for above ground level structures planned near airport facilities. Refer to the FAA Obstruction Evaluation/Airport Airspace Analysis (OE/AAA) for more information and the latest required forms.
The department uses two types of illumination systems:
  • Continuous illumination systems
    – Provides continuous lighting of main lanes, direct connectors, ramp entrances and exits, and merge and diverge areas; and
  • Safety lighting systems
     - Provides lighting at interchanges, highway intersections, or other decision-making points of nighttime hazard. The designer determines the need for safety lighting based on geometric hazards, high crash rates, etc.
Preliminary cross-sections, locations of proposed roadside barriers, topographic maps and information on existing luminaire locations are needed before lighting plans can be developed.
Considerations in designing illumination include:
  • Install lighting systems on eligible roadways where conditions warrant such installation; and
  • Review illumination proposed for residential areas and minimize undesirable impacts on residences.
Determination of the eligibility of the project for illumination and compliance with warranting conditions must be initiated when preliminary illumination locations are established.
4.4.8.3 Intelligent Transportation System Needs
Intelligent Transportation System (ITS) needs should be evaluated and placed on the geometric schematic. ITS uses advanced wireless communications in vehicles and infrastructure to improve safety, mobility, and reduce environmental impact. Real–time data capture and management from vehicles (trucks, transit, cars), mobile devices, and infrastructure improves operating performance of the surface transportation system. Dynamic mobility applications make the system safer, smarter and more economical.
  • Traffic Management Centers (TMC)
     – TMCs manage department ITS equipment. Large metropolitan areas have dedicated facilities, operators, and support staff. Smaller offices are managed by operators with other duties. A TMC works as a central facility with agencies supporting toll collection, vehicular security, enforcement, and safety.
  • Dynamic Message Signs (DMS)
     – Controlled by the TMC. Signs inform motorists of emergency weather hazards, travel-related Homeland Security advisories, or any incidents on the highway. During non-incident times, travel time messages are displayed to assist with congestion management. They give motorists the choice to continue their route or divert to a less congested highway or street.
The District’s Transportation Systems Management and Operations (TSMO) plan should be consulted to determine which ITS elements are recommended.
4.4.8.4 Interstate Access Justification Report
An Interstate Access Justification Report (IAJR) is a comprehensive report that addresses the FHWA Interstate Access Policy Points. For access changes on all Interstates, an IAJR is required to be prepared and submitted for approval by FHWA. Based on the finalized typical sections, horizontal/vertical alignments and intersection evaluation, the need for changes to access can be determined. Regardless of funding, project delivery type (i.e., DBB or DB) or oversight, new or revised access points on Interstate highways must be approved by FHWA.
Revised access is considered to be a change in configuration even though the number of actual points of access may not change.
Generally, any new or revised access to the Interstate system will require FHWA’s review and action, including the following:
  • New freeway-to-freeway interchange;
  • New service interchanges providing access between a non-freeway local roadway network (arterial, collector, or local road) and the Interstate;
  • Modification of freeway-to-freeway interchange configuration, for example, adding new or abandoning/removing ramps, completing basic movements;
  • New partial interchanges or new ramps to/from continuous frontage roads that create a partial interchange;
  • Modification of existing interchange configuration, such as adding a loop to a diamond interchange;
  • Completion of basic movements at partial interchange, for example, completing a partial diamond interchange by adding a ramp;
  • Locked gate access, for example, access via locked gates for emergency response;
  • Access from the street network to special uses lanes, such high occupancy vehicle (HOV), high-occupancy toll (HOT) or truck only lanes;
  • Relocation of a terminal of a ramp to a different local road;
  • Changes in operation of managed-lane access to general-purpose access to the Interstate; or
  • Relocation of a ramp gore along an Interstate mainlane. (Under some circumstances, if a ramp is shifted within the same interchange configuration, which results in ramp spacing that meets FHWA's design criteria, and/or if the interchange is reconfigured in such a way that the travel patterns change with the same number of access points, coordination would be performed with FHWA to determine if an approval through IAJR is required or some other process/coordination).
Each entrance, exit, “locked gate,” new or modified freeway-to-crossroad interchange inside a TMA (urbanized area with a population > 200,000), ramp, or access to a collector-distributor is considered an access point. FHWA must ensure there is either no or only minimal adverse effect on the operation of the Interstate facility.
“Locked gate” access points on the Interstate system are used in remote areas in special circumstances for emergency management, border patrol, utility, or maintenance forces.
Refer to TxDOT’s IAJR Engineering, Operation and Safety Analysis Standard Operating Procedure (SOP) for additional information regarding the IAJR development, submission and review process. Also refer to TxDOT’s TSAP for discussion on evaluation tools for developing the IAJR.
Early coordination between the District, DES, and FHWA is needed to ensure proper preparation, review and acceptance. IAJR approval is contingent on the quality and adequacy of the process and documentation. Preparation, review and approval of an IAJR is typically
18 months
.
If a freeway is planned as a future Interstate, coordinate with DES for IAJR requirements.
All IAJRs must be submitted to DES for review prior to submittal to FHWA. Include this task duration in the project schedule.
IAJR Re-evaluation
The following primary conditions will require re-evaluation of
previously approved IAJRs
:
  • Change in approved IAJR design concepts:
    • Due to environmental impact;
    • Due to final design adjustment; and
    • Due to design‐build proposal.
  • Significant changes in following conditions:
    • Traffic;
    • Land use; and
    • Environment.
  • Time lapse before construction:
    • If the project does not progress to construction phase within
      3 years
      of approval.
Final approval of access cannot precede environmental clearance/NEPA completion.