Mirrors - A Reflection On Blind SpotsThere is no mystery as to the most frequent types of accidents which occur with motorcoaches. Hitting fixed objects, while backing, turning, or moving in and out of loading and unloading locations easily wins the title of "most frequent". To a lesser extent, there are sideswipe accidents related to lane changes. Overwhelmingly, when these events occur (with the exception of backing accidents) they most likely occur along the right side of the coach. And most often, they occur at the back half of the right side of the coach. Pivot points, off-tracking, and tail swing all have a part to play in fixed object accidents. And, blind spots are singled out as the culprit when it comes to lane change related accidents. Of course, backing accidents usually involve a blind spot as well. In almost every one of these types of accidents, the driver is at fault. He/she should have checked before backing; should have set up properly for turns; should have been watching with proper visual scanning techniques to insure knowledge of anything in his/her blind spots; etc. But what about the coach? What about the mirrors? What roll do they play in these events? Mirrors are the eyes of the driver. They are the only means to view to each side and behind the coach. Traditional thinking suggests that mirrors should be adjusted so that the driver can see far enough behind the coach to capture in his/her field of view vehicles as they proceed up and along the coach. At the same time, these mirrors must be adjusted (and especially the right side mirror) to capture in the driver's field of view objects (such as cars, poles, etc.) as the bus moves along and around them. Thus, mirrors are usually adjusted to that the upper half of the drive tires and the remainder of the bus to the rear can be seen. Furthermore, adjusting the mirrors so that you can see just next to the side of the coach in the left side of the right mirror (and the right side of the left mirror) maximizes lateral field of view. With this type of adjustment, the critical blind spots are along the front half of the bus, and especially on the right side. That's what spot mirrors are for. They allow an expended field of view along the side and a wider field of view to each side of the coach. However, these mirrors distort spatial distances between the bus and other objects because of their convex shape. There is no questions that the flat mirror is the best means of vision for drivers to understand or determinethe spatial distance between the bus and other objects as it passes by them or around them. But have you noticed that mirrors are getting shorter. While 12 to 14 in. high mirrors used to be the norm, 6 to 8 in. mirrors are becoming more prevalent. Flat and convex mirrors are housed in the same housing in many cases, even further reducing the height of the flat mirror. The net effect of this has been to reduce the visual area that is critical to the driver. We have learned from working with many bus operators that if the right side mirror can be adjusted so that the ground next to the drive tires can be seen in the bottom of the mirror, many fixed object accidents can be eliminated. We are convinced it is because drivers can literally see the ground and understand the spatial distance between the side of their coach and the object as they move past it. But many flat mirrors on buses today do not allow this adjustment to be made without sacrificing the view of sufficient road behind the coach to see encroaching traffic. The width of mirrors has not changed from our observations and this area of view remains the same laterally, even though there is a shorter field of view because of the decreasing height of the flat mirror. How far forward of the driver's eye location mirrors can be placed is limited because of the structure of the bus. Some models today have the mirror placed far forward of the conventional windshield pillar location thanks to a roof mount extension design; however, these mirrors have presented sight distance issues for drivers in seeing objects moving in front of them from either side - most notably pedestrians. While the science of placing the mirror as far forward of the driver's eye location as possible makes sense, there must be a sensitivity to keeping his direct visual field of vision in front of him as unobstructed as possible. The height of the flat mirror also plays a role in affecting the driver's filed of view. The higher the flat mirror is positioned above the driver's eye height, the greater the downward angle of adjustment needed to obtain the critical field of view along the backside of the motorcoach. As this angle becomes more pronounced, there is less of a field of view behind the motorcoach. How far the mirror is from the side of the bus also impacts driver field of view. The further away from the side of the bus the mirror is located, the more of an inward angle is required to see the critical area at the back side of the coach. This limits lateral field of view for the driver. From where I am sitting, it is time to rethink mirror style and position on motorcoaches. Operators should specify, and manufacturers should provide mirrors that are sensitive to maximizing the driver's field of view:
Motorcoach companies should then institute procedures to assist drivers in properly adjusting mirrors to see critical fields of view as discussed earlier and to remind them of how to overcome blind spots caused by the location of the mirror for their front and side visual view. Using mirror check stations are an excellent way to assist drivers in properly adjusting mirrors before they leave the parking area. And providing them information on mirror adjustment and the proper use of mirrors should be fundamental, no matter how many years of experience your new driver has had. How to operate and adjust the mirror on the model coaches you have is also important information to provide to new drivers or whenever new models are purchased for use. From where I'm sitting, it is time to reappraise sizes, types, and locations of mirrors on motorcoaches to produce the best visual results for the driver. Aesthetics should always be second in importance. Driving down accident frequencies depends upon it. *** Click here to visit the NADME training web site ***
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