Alan Manners Voorhees (December 17, 1922 – December 18, 2005) was a transportation engineer and urban planner who designed many large public works in the United States. Voorhees was born in Highland Park, New Jersey.

During World War II, he left his studies at Rensselaer Polytechnic Institute (RPI) to join the United States Navy as an officer in what was called the "Underwater Demolition Team 11" (UDT-11), a precursor to the U.S. Navy SEALs. He spent much of the war mapping shoreline defenses in the Pacific. After the atomic bombing of Nagasaki, Voorhees' unit was sent in to inspect the city, making him one of the first Americans to see the bomb's aftermath. For his military service he received the Silver Star, the Bronze Star, and the Presidential Unit Citation.

After the war, Voorhees continued his education, graduating from RPI in 1947 and then earning his master's degree in city planning from the Massachusetts Institute of Technology in 1949.

In 1952, Voorhees came to Washington, D.C. to work for the nonprofit Automobile Safety Foundation. While studying traffic in Baltimore, Voorhees developed a mathematical formula to predict traffic patterns based on land use. This formula has been instrumental in the design of numerous transportation and public works projects around the world. He wrote "A General Theory of Traffic Movement" (1956), which applied the gravity model to trip distribution, which translates trips generated in an area to a matrix that identifies the number of trips from each origin to each destination, which can then be loaded onto the network.