Fat-tire biking in Silver Lake Sand Dunes is allowed from Dec. 15 to March 15, 8 a.m. to dusk, within the designated 450-acre ORV area. Riders must enter via the down ramp, and e-bikes are not permitted. No reservations are needed, but a valid Recreation Passport is required for parking; a self-pay station is available. Alcohol and drinking water are not provided, so plan ahead. Gates open daily regardless of conditions, and riders should call 911 for emergencies. Be aware that the dunes change rapidly due to drifts and freezing conditions.