A TSD (Time-Speed-Distance) rally is a type of motorsport rally with the object of driving each segment of a Course in a specified time at a specified average speed. The rally is usually conducted on public roads, but sometimes includes off- road and track sections. Contestants usually compete in teams composed of an amateur driver and navigator. Teams usually start a regularity rally at fixed intervals, creating a field that is spread along the course.
A typical TSD rally may run for a few hours or it may run over a series of stages over a few days. At the start, competitors are usually briefed about the event and are required to submit their cars for inspection. Each team is given a route schedule prior to departure. This schedule contains information that the navigator will use to try to keep to the specified route and it contains information about the designated speeds and times for each segment of the route. On some rallies, more than one type of schedule may be prepared for different types of competitors.
Once a team is prepared, they will usually start the rally at a specific time unique to them. Along the route, the team will encounter marshals. The position of the marshals is usually not known to the teams. The time at which the team arrives at each marshal is recorded and used in the scoring. In some cases the marshals are hidden from view. Teams may also encounter open sections where they are guaranteed not to encounter marshals and are not subject to any time penalties. There may be various other features along the route including points at which teams must wait for an exact time of departure or points at which teams must record their own times.
The organisers can work out the exact times that should be recorded for each team at all the relevant points along the route. The difference between a team's actual times and the correct times determine their penalties (Lateness and earliness both attract penalties). The team with the lowest number of penalties wins.
The road book is a type of map encoded with the correct road to be followed. It counts for all the information about the distances, time and average speed that must be followed throughout the race. It is through these sheets that the navigator will direct, as well as pace, the driver.
It is usually possible to compete in a TSD rally using only a car or a bike and a stopwatch, but many TSD rallyists use various devices in an attempt to reduce their total penalties. The rules of each rally determine which devices are permitted. Some common aids include:
* Odometer: Odometers can range from the odometer included on the dashboard of most cars to specially manufactured rally odometers.
* Speedometer: As with odometers, speedometers used by rallyists range from those built into the vehicle to specially manufactured rally speedometers.
* Stopwatch: Accurate time is essential in TSD rallying.
* GPS: GPS units provide speed, distance and navigational data.
* Computer: Computers ranging from custom-made units to laptops can be used in TSD rallies.
* Applications: Modern day smartphones and tabs owners can use apps like"RallyGDP".