As I was putting my navigation equipment away after the recent 2014 Pumpkin Run rally, I noticed a table that I use that others might find useful in other Time-Speed rallies. I have a table taped to my rally board that provides the time taken to travel short distances. This table is shown below.
Short Distance Time Speed Chart
In Time-Speed rallies, the condition frequently arises where a car will arrive at a stop sign to execute a stop for, say, 15 seconds. With allowances for time lost in stopping and starting, as I explained in a recent post about preparing a Performance Chart, let’s assume that the actual stop time at the stop sign is 9 seconds. However rally competitors have to share the road with other cars and trucks. It is not unusual for cross traffic to prevent the rally car from safely moving forward from the stop sign at the required time. This will result in lost time waiting for a suitable opening in the traffic flow to cross the road.
An alternative to waiting, is to leave early and stop on the other side of the road. This decision would be at the discretion of the driver. The table above will help when it is decided to cross the road early at an opening in the traffic. For example, say we are planning on waiting the 9 seconds before accelerating to 30 miles per hour to cross the road and then follow the road to the next instruction. However seeing heavy traffic, the driver decides to cross the road after stopping for only 3 seconds. Suppose the road is built on a 100 foot right-of-way, then the car might travel 125 feet crossing the road and re-stopping at an appropriate location. Re-starting 125 feet further down the road represents a time gain because you don’t have to spend the time crossing the road. At 30 mph, re-starting 125 feet further down the rally route represents at gain of 2.8 seconds over stopping on the other side of the road. Therefore the re-start waiting time would be (9 + 2.8) 11.8 seconds. Therefore the “Go 30” instruction to the driver would be given 11.8 seconds after first stopping on the other side of the road. While the car is crossing the road, the navigator should be estimating the distance traveled crossing the road.
These decisions need to be made quickly and the navigator might not have time to look up the table and do the calculations before the car needs to move again. When this happens, I would arbitrarily add 3 seconds to the originally planned stop time and tell the driver to “Go 30” at that time. Then once the car gets going, then look up the actual gain based on the table above and make the needed time adjustment further down the course. For example, in our example above the proper gain for crossing the road is 2.8 seconds, but if the car waited the additional 3 seconds from the initial planned stop of 9 seconds, then the car would be running 0.2 seconds late. An adjustment of 0.2 seconds can be made up at the next stop, for example.
Hopefully some other navigators will find this table useful.