Where should you place your warning devices if you must stop on a one-way road or divided highway?

This is required by Federal Motor Carrier Safety Regulations Part 392.22, issued by the Federal Motor Carrier Safety Administration (FMCSA). These regulations also specify where to place warning devices on other types of roadways such as two-way roads and curves. (Those situations are also covered in section 2.5.2 of the Iowa Commercial Driver's License Manual.)