Preventing Vehicle-Aircraft Incidents During Winter Operations and Periods of Low Visibility (2008)

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35 Preventing runway incursions requires a multifaceted approach to addressing all the factors that affect a driver’s ability to accurately identify where he or she may be located on the air- port at any given time. The design of vehicles and equipment are factors to be examined in reducing the possibility of col- lision risk or incursion. VEHICLE DESIGN The design of a vehicle can have a major impact on a driv- er’s ability to operate it safely. A primary factor for pre- venting collisions is the ability to see during winter or low visibility operations. Survey respondents cited blowing and swirling snow, night-time operations, frosted-up windows, and obscured markings and lights as common situations that decreased visibility. Environmental factors affecting visi- bility were previously addressed in chapter four. This chap- ter considers the design of vehicles and its impact on driver performance. A strong opinion of respondents was that high-intensity discharge (HID) lights are the best for cutting through the blowing snow and projecting far down the runway or taxiway. One operator stated that the ability of HID to have a defined illumination was very beneficial, especially if angled down at about 30 degrees from eye level at the cab. The operator stated he only uses the HID lights when plowing because the light is “whiter” and not yellowish like other lights, especially when reflected by the snow. Halogen lights were preferred as the second choice of light. They are less expensive than HID lights, but not as focused in their illumination, and they require a higher lumen output to achieve the same level of illumination as HID lights (47). Regular vehicle lights or spotlights on vehicles were deemed by respondents to be not as effective as either HID or halogen lights. Inadequate information exists on the use of light emitting diode (LED) lights in snow removal equipment or low visibil- ity conditions, though research is advancing on its use in roadway vehicles. One airport identified that their use of LEDs in their rotating beacons were deemed superior to regular beacons. LED backup lights or rear-facing lights are avail- able on some equipment and help prevent rear-end collisions. The accumulation of ice and snow on LED lights is of concern as LEDs do not generate the level of heat to melt ice as do other bulb types. The placement of external vehicle lights has an impact on driver visibility; a location at eye level and angled downward is the preferred choice among respondents. The next choice was placement above the cab. This preference conflicts some- what with a study accomplished in highway use, which stated that lights placed above the cab were not advantageous because they reflected too much light back into the operator’s eyes (48). Lights mounted on top of a plow or sweeper are not perceived to be beneficial either because of the obscuration from blow- back snow. High-visibility lighted (either by fiber or LED) or colored rods on the corners of sweepers and plows were deemed to help with SA for the driver as they could better determine the tracking of the attachment. Due to blowing snow or fog, one respondent said having a rear-facing fog spotlight on the back of the vehicle is important to prevent another vehicle from running into it. One non-hub airport has installed flashing red halogen lights for that same purpose. Another airport has factory-equipped LED lights. Normal vehicle brake or position lights were deemed inadequate for the purpose of providing adequate alert to a fast-approaching vehicle. The type of lights to use and their placement on snow removal equipment are areas for more thorough study (49, 50). Providing small directional glare shields on lights was found to be beneficial. To further reduce glare, it has been found that having just a single spotlight mounted on the passenger side with the driver side spotlight turned off is advantageous (47). If the vehicle lighting is proper, the next design item respon- dents frequently commented on were the windshields. The current design philosophy is to provide as much glass area as possible. For the front windshield, there are three basic designs: forward-sloped, flat, and reverse-sloped. Reversed-slope was respondents’ preferred design during winter operations, because snow and ice accumulate less readily on it. To counter the accumulation, manufacturers have installed washing fluid deluge systems that flood the front and side windshields to remove snow and ice. These were found to be effective by air- port users. The deluge systems pumps heated windshield deicer fluid through a series of nozzles above the primary and side win- dows to rid the windows of accumulations and contaminants. One non-hub airport maintenance department sprays ice melter on the plow truck windshields with a 2-gal. garden sprayer when the wiper blades accumulate ice or slush. They CHAPTER EIGHT VEHICLE AND EQUIPMENT RESOURCES

place the sprayer in the cab so it is available while they are plowing. Wiper blades are an important factor in keeping the wind- shield clean for clear visibility. However, the equipment manufacturers stated they provide only a heavy-duty winter blade that is often no different than what one can obtain for a private vehicle. As a result, ice and snow can still accumu- late on them causing ineffective wiping action and viewing distortion. Older vehicles used to have ridges etched into the glass as a way to vibrate the blade to help it shed snow and ice. Several respondents implied that heated wiper blades were of value, but the most common request from respon- dents was for better wiper blades overall. • “While following the brooms at such slow speeds (they are 10 mph tow-behinds), the windshield on the opera- tions vehicle can get iced up to the point where the wipers don’t do anything. The side windows of the broom’s tow vehicles also get snow-covered.” • “While not one of the above-listed areas, it is helpful to check vehicle windshields before each snow season, especially when using sand. The pitted windshields should be replaced, as necessary, to provide better visi- bility for the next winter season.” Windows can be kept clear of frost, snow, or ice accumu- lation through the use of defroster systems, either electrical or hot air venting. The preference leans toward electrically heated windows and mirrors. Defroster systems can add to humidity buildup inside the cab as a result of the driver’s breathing and body heat. Some airport operators have speci- fied air conditioning units on snow removal equipment for eliminating moisture in the cabin. If not properly designed, defroster systems can contribute to driver fatigue through the generation of excessive noise or fluctuating cabin tempera- tures, and electric wires in the windshield can malfunction. Good lighting and good defrosting are key components for increasing visibility. Another influential factor is the height of the cabin. Plows and sweepers generate swirling or blow-back snow over any attachments and onto the vehicle windshield. As one airport operator mentioned, being able to sit up high and look out and over the swirling snow makes a big difference in his ability to see where he is plowing and to see objects such as signs, markings, and aircraft. The popu- larity of vehicles with the cabins placed as far forward as pos- sible and the engines mounted beneath or behind the cabin support this idea and have environmental noise reduction as an added benefit. Associated with the generation of swirling or blow-back snow (“snow cloud” effect) is the design of the plow blade and deflectors, and the speed capability of the vehicle. All three affect the extent to which snow is blown up and over the blade or brooms and impedes forward visibility. A low-height mold board on a plow reduces the amount or height of swirling 36 snow as compared to a high-straight mold board with a snow deflector, according to snow equipment drivers. But low-center mold boards are not useful at airports that routinely experience high volumes of snow. When used, snow deflectors with trap angles less than 50 degrees can eliminate much of the blow- back (51). Vehicle speed is another factor affecting the amount of swirling snow and resulting snow cloud around the vehicle. The slower the speed, the less the blow-back. Unfortunately, the slower the speed, the longer a vehicle remains on the move- ment areas as a potential hazard to aircraft. The design of the cabin layout has an impact on driver fatigue and distractions. Equipment manufacturers are work- ing to place controls in easy and comfortable reach of the operator. Mounting the controls on a console attached to the seat provides ergonomic benefits. Sound deadening material is being added in some vehicles to better reduce the decibel readings in the cabin. Because of the long periods of sitting, the comfort of the seat is of importance. Most seats installed in snow removal equipment are made of varying stiffness of foam, but air-inflated seat cushions are being researched as an alternative to reduce fatigue and increase comfort (52). Most newly purchased vehicles come equipped with air- adjustable mechanisms. SNOW REMOVAL EQUIPMENT Advisory Circular 150/5200-30, Airport Winter Safety and Operations, provides guidance in the number and type of vehi- cles and appliances for the airport size and operation (12). Sizing of the snow and ice control equipment fleet should be based on the total Priority 1 paved area that must be cleared of snow, slush, or ice within a recommended clearance time. Priority 1 paved areas amount to having cleared one primary runway, taxiway access and egress from that runway to the terminal, and any ARFF access routes. The equipment fleet recommended in the advisory circular is associated with eligibility for federal funding participation. Formulas exist for determining the number of plows, brooms, and blowers to achieve the clearance time necessary for a particular runway or other paved surface areas (53, 54). The acquisition of larger capacity snow and ice removal equipment can help reduce the potential for incursion by hav- ing fewer exposed numbers of operations (55). However, financial considerations may preclude the ability of an airport to acquire more efficient or larger pieces of equipment. Advi- sory Circular 150/5220-20, Airport Snow and Ice Control Equipment, offers guidance on how to select the number and types of equipment necessary to meet recommended clear- ance times (54). The design of vehicles and attachments, the layout and equipping of cabins, and the placement of lights all have an impact on the prevention of incursions. The impact has not been adequately evaluated to identify the best method or

37 practice in the airport sector. Neither is it clear whether research is being applied to vehicle design as much as normal business practices are. One airport conveyed that it was tough to get the manufacturer of their snow removal equipment to accept ergonomic design changes to its vehicle since the pro- duction line was not set up to accommodate such a request. SUMMARY Chapter eight addresses how the design of vehicles and attach- ments, the layout and equipping of cabins, and the placement of lights all have an impact on the prevention of incursions. HID lights were identified as the best lamp type, and the place- ment of lights at eye level angled downward was deemed to be most effective, though the latter is an area needing more study. How to enhance visibility from the cabin is provided through respondent suggestions. The current design philosophy is to provide as much glass area as possible and to fluid deluge systems, good wiper blades, and an effective defroster sys- tem. Another influential factor helping to reduce the risk of collision by enhancing visibility is the height of the cabin and the ability to sit up high and look out and over the swirling snow. Further factors described in the chapter are the design of the plow blade and deflectors and the speed capability of the vehicle.