This report replaces a 2002 document, "A Guide to Updating Highway Emergency Response Plans for Terrorist Incidents." Many states have used the 2002 Guide to institute some kind of emergency response plan; however, the risk environment of threats and hazards has changed since 2002. In addition, new technologies and new, more comprehensive laws, policies, and guidelines require that transportation agencies broaden their operational agenda beyond traffic and weather events to include emergency response planning for all hazards. This 2010 Guide is designed for use by executive management and emergency response planners at state transportation agencies as they and their local/regional counterparts assess their respective emergency response plans and identify areas needing improvement. The 2010 Guide reflects accepted practices in emergency response planning and incorporates advances made over the last decade in Traffic Incident Management (TIM), Emergency Transportation Operations (ETO), and supporting programs. In addition to the introduction, background, and institutional context for emergency response planning, the 2010 Guide has two major parts: Sections 3-5: Design an Emergency Preparedness Program; and Section 6: Resource Guide. The 2010 Guide provides links in its appendices to model emergency operations plans, policy and procedural memoranda, and training and exercise plans.