Toilet facilities are an example of the evolution of crew comfort concerns. They have gone from being absent to standard equipment which improves with new cab designs. For example, Riley (1991) indicates that 35 of 58 locomotive engineers (60%) surveyed thought that the toilet facilities of the SD-60M were better than previous versions. However, there were many comments from locomotive engineers which indicated the need for specific improvements. Apparently, the toilet is often designed to fit the space available rather than designing in the space to accommodate the toilet facility. Complaints that may substantiate this include those of cramped space and lack of heat or ventilation. The cold operating environment also limits design options compared to those available in more controlled conditions. The hot, humid conditions that can exist in the toilet facilities in warm weather are favorable for bacterial and fungal growth. This growth produces persistent odors which are a problem directly and indirectly as they are associated with a lack of cleanliness. Chemicals used in some toilet designs also add odor. Odors represent the most urgent problem with cab toilet  facilities. Some toilet designs recycle water from the holding tank to flush. This exposes the tank contents to the air in concentrations that increase with  use and time and releases stronger odors. The small volume of the typical facility and a lack of, or insufficient ventilation allows odors to build to offensive levels. Even in newer facilities that have ventilation, the ventilation rate is low and the vent arrangement may create dead areas. For example, a lavatory in a modern design locomotive had an inlet vent about three feet above the floor and the outlet at floor level (see Figure 3-4). The upper area, where the user's nose is, is little affected by the air flow. This allows odors to build faster than they are removed. Cab air conditioning, like heat,  is not directly provided in the toilet facilities. Illumination in toilet facilities is often barely adequate. It is provided by a low voltage system that usually  has a single dome light (upper left in Figure 3-4). While this may be appropriate for night use to prevent loss of night vision, it may be too weak for day use. When the cab is brightly lit by the sun, the change when entering the lavatory may cause problems seeing in the low light level. Dim light also strengthens a poor impression of the facility. The light is mounted in the ceiling, generally over the toilet. This places it close to the eye when standing  causes the iris to close, and makes the lower area seem darker still.
 

Figure 3.4

Lack of maintenance is another common comment concerning toilet facilities. Service use of locomotives does constrain availability for maintenance which can extend time between cleaning. While this may play a role resulting in holding tanks that are not pumped often enough or general untidiness, there are also comments that the crews sometimes add to the problem. Since there are no trash receptacles in cabs, crews may use the toilet (or the lavatory in general) as a place to throw trash. Figure 3-4. Vent Locations of Locomotive Lavatory Locomotive cabs can be exposed to subzero temperatures for prolonged periods. This will result in freezing problems with water waste management solutions. This constrains toilet design options. State environmental laws limit how railroads can dispose of effluent. These laws can restrict solutions.

Size:

Woodson (1990) notes that lavatories should not cramp the user. The ceiling height should accommodate the 95th male percentile engineer plus any headgear he may wear. Especially when located in the short hood, current toilet facilities are not very tall or overly spacious. Consideration of the clothing worn during use, which can be bulky, requires more space in locomotives. Riley (1991) cites crew comments that the toilet on the SD-60M, a recent design, is cramped.

Odor:

Bacteria can generate ammonia and methane gasses, both of which can be smelled in low concentrations. These odors are perceived as mildly unpleasant to highly distasteful and are generally associated with unsatisfactory sanitary conditions. Moreover, heat and humidity create conditions in which bacteria can generate significant amounts of gas in just a few hours. This is too fast for cleaning alone to practically remove or prevent. Fungi, like mildew, can also thrive in moist areas wherever organic material is present (e.g., drains and walls) and the result is an additional source of odor. The small volume of cab toilet facilities allows odor concentrations to build rapidly. Ventilation can remove this buildup, but the volume of air movement and inlet/outlet placement impact effectiveness. If the ventilation is inadequate, odors will be present and a perception of uncleanliness can be created. The design of the toilet design must block odors that form in the waste tank from entering the lavatory. Odors can enter the lavatory if there is no physical barrier or the seal is poor. In conventional toilets, water both cleans the toilet and forms a seal against odors from the waste pipe. However, this design presents problems in the temperature extremes that locomotives operate in which force design compromises. Dry toilets, an alternative, can permit solid residues to remain in the bowl. This provides a medium for bacteria and a visually distasteful sight. These design features can require cleaning after each use to prevent odors and other signs of "neglect." A modular self-contained unit that can be removed from the lavatory and replaced with a clean one is another possible approach. The used units can be cleaned later by in-house  or contract services and stocked at terminals for reuse. These toilets are commercially available for boats. Modifications of the current lavatory design may be needed to permit quick and easy exchange at yards. A benefit of this approach is that used units could be removed and replaced with a fresh unit more often than lavatories are currently serviced. Odors may escape into the cab when the lavatory door is opened or if the unvented lavatory door seals are poor. The lavatory location in a well in the short hood creates a pocket which may be under-ventilated and creates a problem in the cab with odor concentration. Under this circumstance, the odor becomes a cab problem rather than just a toilet problem.

As mentioned in the preceding section, it is easy for conditions of "dirtiness" to develop. There is a concept in the security realm  known as "the first broken window." If a window is broken in a vacant building and left unrepaired, it becomes a tacit signal that vandalism is permitted. The situation will rapidly degrade because any addition is merely a change in degree. This applies to all types of unwanted activity: graffiti, littering, etc. This may also apply to cab crews, in that if they perceive the toilet facility as already dirty, a little more mess will not cause a new problem. Results may range from failure to clean an accidental mess to intentional acts. There are two other practical factors that may result in crews not keeping the toilet area clean. The low light level may play a role by reducing vision, and the lack of any other receptacle for trash in the cab leaves the toilet as the best option for trash disposal.

Temperature:

Toilet facilities are not directly equipped with environmental controls, like heat and air conditioning, which are installed in the cab. If ventilated with outside air, the facility temperature and humidity depends on the outside conditions. The lack of heat is worsened by the need to partially undress. Despite the shorter use time, the lavatory comfort requirements for heat or air conditioning are the same as those for the cab. Air conditioning may provide some additional odor reduction by reducing the heat and humidity that favors bacterial growth.