California Department of Transportation


Personnel shall be protected from injury by sharp edges of equipment, fasteners, parts, or cabinets during maintenance. Installer shall deburr all edges 1/32" minimum and shall radius all corners 1/8" minimum.

12.1 General Safety Provisions

  1. Safety criteria shall be applied during equipment hardware design, selection, and construction to eliminate or control hazards that could cause injury to personnel.
  2. Electrical equipment and installations shall be suitable for the roll, pitch, and vibration of a vehicle or other equipment.
  3. All equipment, including switches, fuses, lampholders, etc., shall be suitable for the voltage and current utilized.
  4. Receptacle outlets of the type providing a grounded pole or a specific direct current polarity shall be of a configuration that shall not permit improper connection.
  5. All electrical equipment and circuits shall be clearly marked and identified.
  6. Any cabinet, panel, box, or other enclosure containing more than one source of power shall be fitted with a sign warning persons of this condition and identifying the circuits to be disconnected.
  7. Warning lights/indicators displaying a written word, picture or light shall be visible in all ambient light (sunlight readable) conditions. It is acceptable to use high intensity LED as indicator lights.

12.2 Temperature

At an ambient temperature of 25° C (77° F), the operating temperature of control panels and operating controls shall be not greater than 49° C (120° F) and not less than 12° C (53° F). The temperature of other exposed parts subject to contact by operating personnel shall not exceed 60° C (140° F). The temperature of all other exposed surfaces shall be not greater than 70° C (158° F).

12.3 Electrical

12.3.1 Power

  1. Means shall be provided so that power may be cut off while installing, replacing, or interchanging a complete equipment, assembly, or part thereof. If a main power switch is provided, it shall be clearly labeled as such and shall cut off all power to the complete equipment.
  2. A means shall be provided to protect personnel from accidental contact with voltages in excess of 30 V rms or DC during normal operations or maintenance of the equipment.
  3. After power to the equipment is turned off, the equipment shall discharge all potential stored power within 2 seconds.
  4. Personnel shall be protected from circuits greater than 21 mA AC and 80mA DC.

12.3.2 Protective devices - Interlocks

When a unit is provided with access doors, covers or plates, these access points shall be interlocked as follows:

  1. No interlocks are required when all potentials between 30 and 500 volts are completely protected with guards or barriers.
  2. Bypassable interlocks are required when voltages in excess of 30 volts are exposed as the result of an access door, cover, or plate being opened. Note that these internal voltages are allowed to be unguarded only if they are not exposed during direct support or operator maintenance. The bypass device shall be of such design that closing the associated door, cover or plate shall automatically open the bypass device and leave the interlock in position to function normally. Visual means shall be provided to indicate when the interlock is bypassed.
  3. Non-bypassable interlocks are required when any voltage in excess of 500 volts is exposed as a result of an access door, cover or plate being opened.

12.4 Mechanical

The design of the equipment shall provide personnel maximum access and safety while installing, operating, and maintaining the equipment. Equipment design shall include provisions to prevent accidental pulling out of drawers or rack mounted equipment components. Suitable protection shall be provided to prevent contact with moving mechanical parts such as gears, fans, and belts when the equipment is complete and operating. Sharp projections on cabinets, doors, and similar parts shall be avoided. Doors or hinged covers shall be rounded at the corners and provided with a means to hold them open.

12.4.1 Mechanical Interconnection

  1. The design shall provide positive means to prevent the inadvertent reversing or mismating of electrical connectors, fittings; couplings; fuel, oil, hydraulic, and pneumatic lines; and mechanical linkage. When prevention of mismating by design consideration is not feasible, coding or marking shall be employed with written approval by Caltrans. Coding and marking shall not be approved as a substitute for proper design or items involving explosive, emergency, or safety critical systems.
  2. Power switch location. Equipment power switches shall be selected and located so that accidental contact by personnel shall not operate the switch.

12.5 Equipment Safety Markings

  1. Danger, warning, caution, signs, labels, tags and markings shall be used to warn of specific hazards such as voltage, current, thermal, or physical. The signs, labels, tags, and markings shall be as permanent as the normal life expectancy of the equipment on which they are affixed. Guards, barriers, and access doors, covers or plates shall be marked to indicate the hazard which may be present upon removal of such devices. When possible, marking shall be located such that it is not removed when the barrier or access door is removed. Additionally, hazards internal to a unit shall be marked adjacent to hazards if they are significantly different from those of surrounding items. Such a case would be a high voltage terminal in a group of low voltage devices.
  2. Physical hazards shall be marked with color codes in accordance with ANSI Z535.1 where applicable to electronic equipment.
  3. For potentials between 70 and 500 volts, warning signs, labels, or tags shall be in accordance with ANSI Z535.3, ANSI Z535.4, or ANSI Z535.5
  4. Signs shall be readable from an appropriate distance and shall create no additional distractions nor shall they be hazards themselves.

12.6 Flammability

Materials used in equipment shall, in the end item configuration, be noncombustible or fire retardant in the most hazardous conditions of atmosphere, pressure, and temperature to be expected in the application. Fire retardant additives may be used provided they do not adversely affect the specified performance guidelines of the basic materials. Fire retardance shall not be achieved by use of non-permanent additives to the basic material.

12.7 Ignition Protection

Electrical components that are in a space where gasoline, hydrogen, propane or any explosive fumes can accumulate shall be ignition protected.

Last updated 01/14/04