N.Y. Comp. Codes R. & Regs. tit. 9, § 4111.12 – Programming of drivers.

(a) Drivers may be nominated or changed after declaration by an owner or the owner’s agent or trainer until “programming time,” the day and time established by the presiding judge at the beginning of the meeting and posted in the declaration room. At programming time it shall be the responsibility of the trainer to make any nomination or change necessary to complete the program after which such nominations or changes shall be made by the judges. Failure to make a necessary nomination or change by programming time shall subject the trainer to fine and/or suspension.
(b) After programming time, but before wagering has begun on the horse, if the programmed driver is unable to drive or has not reported to the paddock judge at least 10 minutes before such wagering has begun, the judges shall substitute another driver therefor, if feasible.
1. (1) After wagering has begun on a horse, if its programmed driver is unable to drive the horse shall be scratched unless:
  1. (i) the race is an early closing event or stake;
  2. (ii) the driver is unable to compete because of injuries suffered in a previous race on the same program; or
  3. (iii) the judges believe a scratch of the horse will not be in the public interest.
2. (2) In the circumstances enumerated herein the judge may appoint a substitute driver.
(c)
(d) Compensation for an assigned or substitute driver may be fixed by the judges.