There are a lot of really good NCHRP reports on traffic safety, but they are pretty specific in addressing a specific aspect of safety. The Institute for Transportation at Iowa State University has put together a great summary on traffic safety - the Traffic Safety Analysis Manual.
The target audience for the Manual are public agency engineers, not specifically traffic engineers. The intent is to provide a basic primer with a lot of useful checklists and a step by step process for improving safety. The authors hope city and county staff engineers will be able to use the Manual to improve safety in their jurisdiction.
The first few chapters are pretty Iowa specific, but the later chapters provide general information any engineer can use. My favorite sections are the checklists of Issues/Countermeasures on pages 40-44 and 80-84. This is a very handy reference. Check it out.