Highway engineers and administrators need to make decisions about safety. The Highway Safety Information System (HSIS) in the U.S. helps them understand how road design affects safety by studying both crashes and safe stretches of highway. The system collects data on factors like median design and lighting on urban freeways. This data can be used to make transportation decisions that consider safety along with traffic flow and cost. The HSIS provides valuable information for planning multi-state safety databases and can be accessed by safety researchers for international research.