Roads through protected areas are generally believed to have many adverse environmental effects but there are few examples of road building being halted for environmental reasons. In Katavi National Park, western Tanzania, plans to upgrade a murram road connecting regional capitals have been stopped in favour of retaining the sanctity of the protected area. Despite empirical evidence suggesting upgrading would damage trees, increase traffic, adversely affect large mammals, and result in more litter, the decision not to upgrade was likely made for general environmental and sociopolitical reasons rather than on consideration of ecological data per se. This suggests that conservation scientists, while remaining independent, need to work with politicians to achieve environmentally friendly outcomes regarding tropical highways.