Wikipedia
Quadrasteer
Quadrasteer is the name of a four wheel steering system developed by Delphi Corporation while under the ownership of General Motors for use in automobiles. It was available as an option on GM's full-size pickup trucks and 2500 Suburbans for model years 2002 through 2005.
Such a system can be a useful feature to people who tow regularly, as it enables a person to turn their vehicle in tighter spaces than if they had a regular steering system. It was costly, adding as much as $5,600 initially (later reduced to about $2,000 and then $1,000 to boost acceptance) to the price of the vehicle. Many people, especially those who tow boats, fifth wheels, or other large equipment found the system useful enough to justify the expense.