· Cab glazing should be designed to reduce heat loss by radiation, conduction, and by air infiltration at poor seals.

· Cab floors should be insulated to prevent ambient heat loss and conduction from feet when standing; and walls should be insulated to reduce radiation.

· Sidewall convectors or other means to create a thermal barrier should be standard equipment rather than options which can be omitted.

· Cabs should provide a means to add humidity to the heated air to improve comfort, reduce skin and membrane drying, and aid dust settling.

Human Factors Guidelines for Locomotive Cabs

· Positive cab pressure should be maintained to reduce infiltration of outside contaminants and drafts.

· The ability to reduce humidity is important in areas with high temperatures and high dew points.

· The air conditioning system should not discharge directly on cab occupants.

· Windows should be provided with movable visors or tint shades to reduce radiant heat gain.

· Air conditioning should be used to decrease use of both open windows and ventilation systems and to reduce interior noise.

· Air conditioning can reduce noise levels due to open windows and other external ventilation systems. Use of a ventilation system and open windows during warm weather adds significantly to noise levels. They can create noise directly and provide a clearer path for entry of outside noise.

· Insulation from exterior sound may hinder hearing of exterior noises that provide important cues (e.g., horn loudness, torpedoes). Use of exterior sensors and interior annunciators may be required to compensate. · Active noise cancellation may potentially provide important benefits and complement current noise reduction methods. Combined with relatively low cost and installation ease, this evolving technique should be investigated.

· Toilet facilities should be designed carefully (e.g., avoid inside corners that create pockets, provide a floor drain) and should be made of appropriate materials (e.g., nonporous) to permit easy cleaning/disinfecting.

· “Locomotive crew may experience significant repetitive mechanical shocks and/or vibrations which are known to affect comfort, safety and health. The motions of interest are those along the vehicle's three translational axes (X, Y and Z) and roll motions about the vehicle's direction of travel. There is evidence that roll and lateral motions are particularly important with regard to crew comfort. Guidance for the evaluation of mechanical shock and vibration can be found in the ISO's (International Organization for Standardization) Document 2631. Emerging research suggests that repeated longitudinal shocks, such as those encountered in switching operations, may also negatively influence crew health.”

· Muscles are used to overcome vibration effects on the body. This can produce fatigue and overuse syndromes, depending on the effort required and length of exposure.

· Position (standing versus seated) and direction of the vibration (vertical versus horizontal) are also important factors. In general, sitting is more stressful than standing while horizontal vibration is slightly more bothersome than vertical vibration.

· In terms of loss of comfort, the human body is sensitive to vibration in the 0.4 to 20 Hz range. With regard to vertical  vibration, the area of greatest sensitivity between 4 and 10 Hz, very low frequency vertical motions (0.1 to 0.5 Hz) are not experienced as vibration but may result in motion sickness.

· Use of dampers at the seat post can reduce the vibration exposure to the operator. However, this can create a difference in relative vibration of the operator and the controls and displays. Operation and legibility problems can result if the difference is large enough.

· Active systems can provide greater vibration control than passive systems. They can be potentially applied to locomotive suspension, cabs, or seat posts.

· User population sizes should be used to design the cab with the male 95th percentile dimensions used to set clearances and the female 50th percentile dimensions used to set reach envelopes.

· Enough space should be allocated for each cab occupant: 65 sq.ft. is a minimum amount of floor space. Comfort facilities (toilet, water cooler, storage, refrigerator, etc.) should be located out of the main area of the cab and not counted as crew space.

· Auxiliary items, such as a first aid kit, flares, torpedoes, and fire extinguisher, should be mounted where they are accessible, but do not impede movement in the cab.

· Cab design should consider ease of maintenance and cleaning.

· Equipment failures should be readily identifiable and only cause loss of function that the engineer can safely handle (failsoft). No single failure, or likely combination of failures, should create an unsafe loss of function (failsafe).

· Designing for extremely large individuals is appropriate when a design feature must accommodate most of the population (e.g., a doorway).

· Designing for an adjustable range is permissible when features can be easily tailored to the individuals who use them (e.g., seats, keyboards).

· Designing for the average individual is appropriate in noncritical situations, where designing for an extreme is inappropriate and where adjustability is impractical (e.g., a toilet seat).

· The primary displays and controls should be placed so that the engineer may view them without changing eye or head position from the normal line of sight.

· Controls and displays of secondary importance may be located so that eye movements are necessary, but head movements are not.

· Padded forearm supports should be used to relieve pressure at the shoulder and elbow.

· Design the workstation so that the engineer's elbows remain flexed (bent) and allow for control activation.

· Consider providing a workspace that allows both sitting and standing.

· Labels should be designed to survive wear and damage under normal operating conditions.

· Use words and abbreviations that are commonly known and meaningful to the user.

· Instructions should be easily seen.

· Wording of labels or instructions should be concise.

· Labels should be located next to or on controls.

· Danger signs should use white lettering on a red background.

· Workspace and access areas should allow adequate room for needed body motions such as crawling or kneeling.

· Those components most likely to fail and those most critical should be the most accessible.

· Make access panels accessible with common tools.

· Consider modular design and throw away units to minimize the skill level needed to maintain the equipment and reduce the impact on related sub-systems or components.

· Use self-adjusting mechanisms where possible.

· Use self-lubricating sealed assemblies with throwaway replacements.

· Make stored materials, assemblies and spare parts easily accessible.

· Clearly mark storage locations and parts.

· Make retaining or load securing devices easily removable.

· Make removable parts easily accessible.

· Make misconnection of parts impossible through use of keyed interconnections.

· Design gaskets and seals to be easily replaced without completely removing or disassembling other equipment.

· Use quick disconnect electrical devices where units are replaced frequently.

· Use hinges, latches or catches to reduce handling and storage of covers.

· Design covers to avoid holding dust and dirt.

· Design cables or wire runs without bends and locate them to prevent stepping on them.

· Design both ends of cables and plugs to prevent misconnection.

· Route wiring away from lines that carry combustibles to prevent fires from sparking.

· Design items over 45 pounds for two-man operation.

· Enable use of common hand tools to repair or replace defective items.

· Minimize the number of special tools required. When they are required, make them captive to avoid being misplaced.

· Provide quick and positive identification of malfunctions and components.

· Minimize the need for special test equipment.

· Design major assemblies to be completely inspected by means of removable housing.

· Reservoirs, gauges, meters should be visible without removing panes or other components.

· Visual access should be available for maintenance in progress.

· Make seals and gaskets easily visible after installation.

· The placement of doors should consider post accident evacuation. Rear doors leading outside offer ready exit routes in most, but not all, accident scenarios. The piling of cars on and around the locomotive may in some circumstances block exits.

· Doors should open outward to permit easier pre-accident exits. This also eliminates the need for a clear area in the cab to allow an unobstructed inward swing.

· Nose doors should be offset to reduce cab drafts. Doors that directly access the front of the locomotive are susceptible to drafts and are less crashworthy.

· Door latches should be examined for potential hand pinch areas in their range of motion.

· The bottom edge of doors should clear the walkway they open over to reduce the obstruction by ice and snow.

· The nose door should include a small sight glass to see if there is somebody that could be struck when opening the door.

· A wide opening or pop out side window or 25 x 25 inch roof hatch may be desirable to provide an additional evacuation

route.

· Visibility requirements should be determined by the objects that must be seen and the human and train reaction lags in the control actions that the objects trigger.

· Too much window area can have drawbacks. Examples are radiant heat gain, heat loss, glare, reflections, vulnerability to thrown rocks, and now, gunshots.

· Accommodate the engineers visual requirements in both directions if the locomotive will operate in both directions. Use of a long haul locomotive for switching or long hood forward operation does not fully meet the engineer's visual requirements. Properties that use bidirectional travel for long periods or eliminate switchers for financial or other reasons create visual problems for engineers.

· Locomotive seats should be cushioned at least 3 inches thick, use the buttocks for primary support, exert little pressure on the thighs especially at the front edge, support the lower back and have arm rests 4 inches wide and 13 inches long.

· Seat height should be adjustable from 16 to 19 inches in steps no larger than 1 inch. Seat should adjust forward and back at least 4 inches from the 50th percentile position.

· The seat cushion should be contoured for buttocks and the back for spinal curves in order to even pressure and provide support. Provide adjustable  lumbar support to increase support and comfort level.

· A rectangular seat pan with elevated sides is preferable to a round seat pan. The lateral support offered reduces muscular effort in curves or lateral cab movements and accommodates legs when spread at a comfortable angle.

· A continuous balance seat pan may correct this by tilting to relieve spinal pressure when leaning. The need to lean forward to operate controls and twist and lean to look out side windows may negate the best conventional seat design because it creates strain on spinal discs.

· The ideal seat adjustment mechanism is easy to use, reliable, and wear resistant. A swivel may be needed to access the seat and to accommodate the need to turn to look to the back and sides. The seat covering should be made of fabric or perforated leather to reduce perspiration and heat buildup.

· Non-seat characteristics can have a direct or indirect impact on the seated position or use of the seat and need to be considered to determine seating comfort. Non-seat factors include: leg room, knee room, availability of footrests, clearance from sidewall, vibration levels, ease of entry/exit, clearance when swiveling, visibility, and reach-to-control distance.

· Place motion controls directly in front of the engineer with the brake module on the left.

· Controls should be arranged to minimize engineers changing their position solely to operate a control. Position all controls so that, in manipulating them, operators do not appreciably move their nominal eye reference and possibly miss seeing important events occurring outside or on the principal  internal display (Woodson, 1992).

· Controls should be arranged according to the order they are expected to be used. Tracing the sequence of control use will help identify poor arrangements.

· Controls should be consistent with normal limb motions. This means that where arm motions are needed they should be forward and back, not sideways. Controls that have a similar function or purpose should be grouped together.

· The panel should contain an end-of-the-train unit alarm and a built-in lamp test function.

· Non-speech signals should be in the 200 to 5,000 Hz range and ideally in the 500 to 3,000 Hz range. Loudness of sounds used should be consistent with the ambient sound level, but not so loud that they startle or disrupt the proper response. Loudness should also be consistent with the  urgency of the message.

· For the vigilance system, the audio alarm and visual alert should be near the windshield since the engineers attention should be directed towards the outside. For the engine monitoring system, the warning sound should come from somewhere near the warning advisory panel. Avoid the use of sounds that could be confused with operational or malfunction noises (e.g., air brake releases, pump operations, sand discharges, etc.). Limit the selection of advisory sounds to no more than four to ensure proper identification.