Races are decided by the elapsed times of the different teams to negotiate the measured course. Only one sled is permitted on the course at a time. An electric clock in the timing room at the finish line is actuated by impulses from electric eyes at the start and finish. As the front of the sled crosses the starting line the “eye” at that point transmits its impulse to the clock, which starts recording on a tape, run by a printer connected to the clock, the elapsed seconds and minutes as the sled makes its run. As the front of the sled crosses the finish line, the electric eye at that point stops the clock and records on the tape the finish mark to the nearest second. The chief timer then measures this mark to the last recorded second and, by means of a Vernier scale, comes up with the elapsed time to the hundredth of a second. As races are often won by hundredths of a second, this measurement must be accurate. The writer acted as chief timer in the United States Olympic tryouts in 1935 when the 2 leading teams were exactly tied in elapsed time to the hundredth of a second at the end of 4 heats. The official time of each was 7 minutes 45.69 seconds for 4 mile-and-a-half heats. In such case the rules provide that the team with the fastest singled heat be declared the winner.
In addition to the electric timing, three stop watches time each heat of each sled and this time is recorded so that if by any mishap the electric timer ceases to function, the watch time may be used.
In championship races each sled makes 4 trips down the run and the combined time of the 4 heats constitutes the official time for the race. If weather conditions or other contingencies pre-elude the possibility of each team finishing 4 heats the race may be declared official after the second heat. Even if all sleds have finished 3 heats and possibly some of them have made their fourth run when the stoppage occurs the third and fourth heats are voided and the race reverts to the first 2 heats. This is because the early starters have an initial disadvantage through having to break in the track. This disadvantage is equalized in the later heats of a 2- or 4-heat race through the device of the order in which sleds start in a heat. However, a fair starting order cannot be worked out for a 3-heat race.
All sleds and crews entered in races must conform to certain restrictions promulgated in the rules of the F.I.B.T. The maximum weight of sleds must not exceed 507 lbs. for the 4-man sled or 363.6 lbs. for the 2-man. The length of the sled is restricted as is the width between runners, only one width being permitted. Minimum gauge of runners if prescribed. Only sleds constructed for the sitting position of crews are permitted. Crews may not lie prone on the sled. The latest rule change is a restriction of weights of crews. On the 4-man bob the weight of the crew is limited to 880 pounds and on 2-man crews to 440. However, if the total weight of the crew falls short of these limits, ballast in the form of lead bars may be added to the sled to equalize the chances of a light crew against heavier opponents.