[2] Rubber hoses are stretched across a road and wheels of passing vehicles create air pulses that are recorded by a roadside counter.

Since Gates and Allen did not know how to build a computer capable of processing data on paper tapes, they recruited Paul Gilbert to help in building a prototype that can manually read the hole-patterns in the paper tape and transcribe the data onto computer cards.

[4] The next step was to build a device to read the traffic tapes directly and eliminate the tedious manual work.

Gates and Allen had a friend, Paul Wennberg, who, like them, loitered at Control Data Corporation near the University of Washington, cadging open time on the mainframe computer.

Wennberg talked to his friend, Wes Prichard, who suggested to Wennberg that Gates and Allen head over to the UW Physics building, now known as Mary Gates Hall,[5] to talk to Paul Gilbert, another electrical engineering student, who worked in the high-energy tracking laboratory.

"Later, the State of Washington offered free traffic processing services to cities, ending the need for private contractors, and all three principals moved on to other projects.

The real contribution of Traf-O-Data was the experience that Gates and Allen gained, skills they used to write Altair BASIC for the MITS Altair 8800 computer: "Even though Traf-O-Data wasn't a roaring success, it was seminal in preparing us to make Microsoft's first product a couple of years later.

We taught ourselves to simulate how microprocessors work, using DEC computers, so we could develop software even before our machine was built."