That only leaves a bicycle or running.
The cheapest form of personal transportation available is typically walking.
the cheapest transport is Waterways
I think train
Because it is the cheapest way of transport.
bus
The cheapest bus transportation from St. Louis to Washington DC would be taking the MegaBus. Tickets for a MegaBus can start as low as $1.
Because it is the cheapest way of transport.
Coach or bus.
U Haul!
Transit Van Shuttle Services
Shanks' mare.
Backpacking it, staying in hostels and using the slow trains for transportation makes for the cheapest travel around Europe.