# At the End of a Slippery Slope: A Pilot Study of Deceleration Mats for Snow Tubing
## 1 Introduction  
Snow tubing is a recreational adventure sport in which a participant rides downhill over snow on an inflated tube. There are varying levels of sensation seeking amongst snowsports participants [1] and snow tubing allows individuals to participate in snowsports who may not otherwise be interested or capable. Though many people ride snow tubes on open, unmanaged land, a growing number of people in the USA are snow tubing at ski areas or dedicated snow tubing facilities where snow tube riders descend in lanes that are separated by berms. The lanes and berms are built and maintained using typical snow grooming equipment. According to the National Ski Areas Association Kottke report [2], there were more than 85 snow tubing hills operated by ski areas during the 2018/2019 season in the USA, with over 1.75 million custern visits.  
A commercial snow tube is different from a typical consumer tire innertube. A commercial snow tube is typically a butyl rubber inflated ring torus with a fitted cover consisting of a plastic bottom and a nylon canvas top surface, with webbing handles for a rider to hold. A commercial snow tube cover can have a bottom surface that is a hard polymer (such as polyethylene or polyester) or a soft, urethane-coated vinyl.  
Snow tubing operations have mechanical systems, such as a conveyor lift, that carry snow tubes and riders uphill to the top of the lanes. To descend, a snow tube rider sits in the center of the ring torus or lies chest down on the top of the snow tube and descends thehill in the tubing lane. To facilitate downhill acceleration of the snow tube and rider (due to gravity), snow tubing requires a low coefficient of friction (COF) between the snow and the bottom surface of the snow tube. At the end of the downhill section, the snow tube and rider decelerate and stop in an area called the run-out. Design of the run-out (length, slight elevation increases, deceleration assistive devices, etc.) is important because a rider (and others around the run-out area) may be at increased risk of injury if the snow tube and rider continue past the designated run-out area.  
The COF between the snow and the bottom surface of a snow tube changes with snow conditions, snow types, and other environmental factors. For example, the COF would be different for fresh powder snow when compared to granular, hard packed snow. According to the scientific literature, the COF between snow and polymers (such as those found in skis and snowboards) is dependent on many factors that include the characteristics of the snow, water content of the snow, temperature, speed, etc. [3,4] The complex interactions of these variables can change quickly (within minutes) and the COF between snow and a snow tube can vary significantly over the course of a day. A change in COF will affect the speeds of snow tube riders as they descend, the speed at which they enter the run-out area, and the distance traveled in the run-out area. Because of the variability in COF for snow tubing, many ski areas in the USA use rubber deceleration mats in the run-out area to slow snow tube riders.  
According to some members of the snowsports community, snow tubing deceleration mats slow snow tubes too rapidly and makes riders more likely to fall off their snow tubes (that is, destabilizing the riders). Others believe that deceleration mats do not slow snow tubes enough (if at all) and have suggested that snow tubing operators fold deceleration mats to slow better snow tubes and riders. To our knowledge there has been no scientific study of the efficacy of snow tubing deceleration mats that could help guide the design and analysis of a snow tubing park. To this end, we examined the deceleration and effective COF produced by snow tubing deceleration mats by measuring directly their effect on snow tubes riders.