A modular multilane steel freeway bridge has been constructed from surplus railroad flatcar decks. It can be erected on-site in a few days’ time. It has been built and static-load tested for emergency freeway bridge repair, This inexpensive modular bridge may also have broad application around the world for low-cost bridges in areas where funds are limited. On the basis of static-load testing performed by the California Department of Transportation and computer dynamic analysis, this simple modular-design concept has the potential of providing a strong bridge that can withstand the severe aftershocks expected immediately after a major earthquake.