OSHA requirements are set by statute, standards and regulations. Our interpretation letters explain these requirements and how they apply to particular circumstances, but they cannot create additional employer obligations. This letter constitutes OSHA's interpretation of the requirements discussed. Note that our enforcement guidance may be affected by changes to OSHA rules. Also, from time to time we update our guidance in response to new information. To keep apprised of such developments, you can consult OSHA's website at https://www.osha.gov.

March 13, 2000



MEMORANDUM FOR: RUTH McCULLY, Regional Administrator
Boston Regional Office
Directorate of Construction
SUBJECT: Tunnel Illumination Interpretation


In your February 8 memo you ask several questions regarding the application of the underground lighting requirements to a 9-mile-long tunnel project. You explain that, in the next stage of the project, 52 diffuser plugs will be removed. The ventilation and lighting systems used during construction of the tunnel have already been removed. To remove the plugs, a ventilation system may have to be installed the length of the tunnel and then (once the work is completed) removed by a "backing-out" process. Our response to your questions is limited to this specific scenario.

Question 1: Does the transport of workers through the tunnel fall within the definition of "work in progress"

The underground construction standard cross-references the lighting requirements of §1926.56(a). That standard states: "Construction areas, ramps, runways, corridors, offices, shops, and storage areas shall be lighted to not less than the minimum illumination intensities listed in Table D-3 while any work is in progress [emphasis added]." Table D-3 requires 5 foot-candles of light in "tunnels, shafts, and general underground work areas...."

Because work includes the necessary activity of gaining access to the work station, there would be "work in progress" when employees are traveling through the tunnel to or from a work station. Five foot-candles of illumination would be required at least in the vicinity of such employees. So, in your scenario, the areas where work is "in progress" are the areas where the workers will be performing their work tasks as well as the distance in front of (and around) the vehicle necessary to travel safely.

Question 2: Is illumination provided by vehicle-powered lights (such as lights powered by a vehicle's electrical system) an acceptable method of meeting the §1926.56(a) illumination requirements in tunnel areas through which workers are transported, but which are not otherwise active work areas?

The standard does not limit the type of lighting system that may be used to attain the 5 foot-candles. Depending on the circumstances, illumination from vehicle-powered lights may be sufficient.

In addition to the basic requirement for illumination, §1926.800(g)(4) requires that each employee underground shall have an acceptable, portable hand lamp or cap lamp for emergency use (an emergency lighting system can also be used).

Question 3: Can the lighting in an active work area be supplied power from portable diesel generators located in, or adjacent to, the work area? Alternatively, must the electric power be supplied from a more reliable source outside the tunnel?

Neither the underground construction standard (§1926.800) nor the cross-referenced provision for illumination (§1926.56(a)) specifically address the extent of reliability required of the lighting source. Note that §1926.800(l)(2) limits the type of portable lighting equipment that is permitted to be used within 50 feet of an underground heading. Portable lighting is therefore permitted (with specific limitations) under the standard.

Because of the particular circumstances of underground work, it is essential that the lighting system used be reliable and not subject to interruption or failure. If interruption or failure is foreseeable, a back-up system (other than the emergency system required by §1926.800(g)(4)) may be necessary.

Question 4: What constitutes "general underground work areas" that must be illuminated to 5 foot-candles?

These areas are both those described in our response to Question 1 and where employees are performing their underground work tasks.





1 OSHA adopted §1926.56(a) with Table D-3 directly from section/paragraph 8.2 of the 1968 Bureau of Reclamation (Interior Department) standards/regulations in 1971. [ (Back to text) ]

[Corrected 5/28/2004]