(a) Application of regulatory and advisory speeds.
  (1) Introduction.
    (A) When an engineering and traffic investigation shows that the statutory speed limits are no longer applicable for the existing conditions, the prima facie maximum speed limits should be altered accordingly with a speed zone.
    (B) The types of speed zones are as follows:
      (i) regulatory; and
      (ii) advisory.
    (C) Advisory speeds may be posted within regulatory speed zones to advise drivers of a safe operating speed.
  (2) Regulatory speeds.
    (A) Regulatory speed zones should be applied only to those locations and sections of highways which are not dealt with adequately by the general statewide speed limits, and they should be indicators of the speed limitations imposed by physical and traffic conditions at such locations.
      (i) Speed limits are determined by specific roadway and traffic conditions.
      (ii) Speed limits should not be lowered to the extent necessary for a driver to avoid a collision with a pedestrian or other motorist who is entering or crossing the highway in violation of an existing traffic regulation.
    (B) The following factors affect roadway safety and, therefore, should be considered when establishing speed limits:
      (i) horizontal and vertical curves;
      (ii) hidden driveways and other roadside developments;
      (iii) high driveway density;
      (iv) crash history along the location;
      (v) rural residential or developed areas; and
      (vi) lack of striped, improved shoulders.
  (3) Advisory speeds.
    (A) Advisory speeds are the desirable speeds for curves, intersections, or other locations where design standards or physical conditions of the roadway restrict safe operating speeds to values less than the maximum legal speeds or posted regulatory speed limit.
    (B) The following Figure illustrates the use and application of warning signs with advisory speeds. For additional information on determining advisory speeds, see §25.25 of this subchapter (relating to Application of Advisory Speeds).
Attached Graphic
  (4) Advisory speed sections in regulatory zones.
    (A) If an advisory speed is located within a regulatory speed zone, it is not necessary to lower the zone speed to conform with the advisory speed. In erecting the signs, care should be taken to not erect a regulatory speed limit sign so near the advisory speed sign that drivers may become confused by two different speed values.
    (B) An advisory speed within a regulatory speed zone should not be posted for a value higher than the posted speed of the regulatory speed zone. Care should also be taken not to place a regulatory speed sign between an advisory speed sign and the location to which the advisory speed applies.
  (5) Regulatory versus advisory speeds.
    (A) Advisory speeds are determined primarily by physical and design characteristics of the roadway.
    (B) The setting of regulatory speeds, while also affected by physical and design factors, is determined in large part by existing free flow traffic speeds.
    (C) A commission minute order, or city or county ordinance or resolution is not required for advisory speed zones, but is required for regulatory speed zones.
(b) Regulatory speed zones.
  (1) Introduction. A regulatory speed zone is the application, by commission minute order or city or county ordinance or resolution, of posted legal speed limits to sections of roadway where the numerical values of these special speed limits have been determined through engineering investigations of traffic and physical conditions.
  (2) Within incorporated cities.
    (A) The commission has the authority to:
      (i) alter the speed limits on highways within the corporate limits of cities; or
      (ii) override a speed limit set by city ordinance or resolution on such highways.
    (B) The department should make studies and present recommendations to the city for its acceptance and passage of a city ordinance or resolution to establish city speed zones.
  (3) Highway approaches to incorporated cities.
    (A) Speed zoning of highway approaches to cities should find its greatest application near the cities where built-up business and residential areas require speeds below the statewide maximum for safe operation.
    (B) Graduated or buffer zones may be used on approaches to cities to accomplish a gradual reduction of highway speeds to the speed posted at the city limits.
  (4) Minimum speed limits.
    (A) The need for minimum speed limits should be determined through an engineering and traffic investigation. When such a speed is justified, it should be regulated in the same manner as maximum speed limits are regulated.
    (B) Minimum speed limits are generally justified when studies show that slow moving vehicles on any part of a highway consistently impede the normal and reasonable movement of traffic to such an extent that they contribute to unnecessary lane changing or passing maneuvers.
    (C) The maximum speed limits and the need for minimum speed limits must be determined from the same speed check data. Section 25.23(b) of this subchapter (relating to Determining the 85th Percentile Speed) contains a discussion of the 85th percentile speed and minimum limits.
    (D) MINIMUM SPEED LIMIT signs (R2-4) shall be displayed in conjunction with and beneath the MAXIMUM SPEED LIMIT signs (R2-1) or as an integral sign (R2-4a).
  (5) Regulatory speed signs (R2 Series).
    (A) Signs for regulatory speed zones shall be:
      (i) from the R2 series as shown in the Texas Manual on Uniform Traffic Control Devices (TMUTCD); and
      (ii) of the appropriate design, including size, text, and color.
    (B) At the end of speed zones on conventional highways where the maximum legal rural speeds are permissible, an R2-1 SPEED LIMIT XX sign, or larger size sign showing those limits, should be erected in accordance with the TMUTCD.
    (C) At the end of speed zones on freeways where the maximum legal rural speeds are permissible, the R2-1 SPEED LIMIT XX sign showing those limits shall be erected.
    (D) The following Figure illustrates the typical location and frequency of signs for regulatory speed zones.
Attached Graphic
      (i) Distances shown between speed limit signs are examples and may be greater, depending on the results of speed checks.
      (ii) Posted regulatory speed limits will be based on the 85th percentile, as described in §25.23(b) of this subchapter.
  (6) Signs within cities. The department may erect and maintain speed limit signs on highway routes within the corporate limits of cities where speed limits based on the results of an engineering and traffic investigation are established.
(c) Construction regulatory and advisory speeds.
  (1) Introduction. Traffic control in work sites should be designed on the assumption that drivers will only reduce their speeds if they clearly perceive a need to do so. Reduced speed zoning should be avoided as much as practicable.
  (2) Advisory construction speeds.
    (A) Advisory speed plates (CW13-1) in conjunction with construction warning signs can often be used more appropriately than construction regulatory speed signs.
    (B) The advisory speed plates are intended to supplement construction warning signs advising drivers of a safe speed to drive through the section signed. See Part 6 of the Texas Manual on Uniform Traffic Control Devices (TMUTCD) for sign detail and typical application diagrams.
    (C) The advisory speed can be altered as needed by project conditions, and several different advisory speeds can be used for varying conditions throughout the project.
  (3) Regulatory construction speed zones.
    (A) Regulatory construction speed limits should be used only for sections of construction projects where speed control is of major importance and enforcement is available.
    (B) Regulatory construction speed signs (R2-1) should be removed during periods when they are not needed in order to minimize interference with traffic. See Part 6 of the TMUTCD for sign detail.
Cont'd...