Please see rule RSC1:
<RSC1> All rules, scoring, and field layouts from previous sections apply to the Skills Matches, unless otherwise specified.
There are no RSC rules that specify a number of Drivers for Driving Skills Matches. Therefore, rules G6 and G7 would apply, and are partially quoted below for reference:
<G6> Two Drivers per Team. Each Team shall include two Drivers. No Driver may fulfill this role for more than one Team at any given event, or in a given season. Teams with only one Student in attendance at an event are granted an allowance to use another qualified Driver from the event. That Driver may now only drive for the team the Driver is subsuming in for, for the duration of the event.
<G7> Drivers switch Controllers midway through the Match. In a given Match, no Driver shall operate a Robot for more than thirty-five (0:35) seconds. The two Drivers must switch their controller between twenty-five (0:25) seconds and thirty-five (0:35) seconds remaining in the Match. The second Driver may not touch his/her Team’s controls until the controller is passed to him/her. Once the controller is passed, the first Driver may no longer touch his/her Team’s controls.
Note: If only one Driver is present (i.e. the Team has not exercised the allowance in <G6>), this rule still applies, and they must cease Robot operation after thirty-five (0:35) seconds.