From the US Department of the Interior: We all love desert tortoises, but if you ever encounter one in the wild, please leave it alone. If a tortoise is scared, it will void its bladder, potentially losing a year’s worth of fluids that it needs to survive.
When driving in desert areas, it’s essential to be vigilant. Tortoises and other wildlife may be crossing the road. In the spring, tortoises emerge from their burrows in search of food and a mate. These ancient creatures, who have roamed the Earth for 15-20 million years, are not accustomed to navigating around vehicles. They move at an average speed of 0.2 mph and do not have a ‘jaywalk jog.’
If you see a tortoise in the road, stop and give it plenty of space to cross. If it is safe, try to alert others. Thank you for helping us protect these ancient reptiles! 
Photo by Brad Sutton / NPS