Ÿ The design standards for the Pennsylvania Turnpike were a marked change from previous highway construction efforts. The original limits were from Middlesex, west of Harrisburg, to Irwin, east of Pittsburgh, a distance of 160 miles.

Ÿ Plans called for a 200-foot right of way with two 12-foot lanes of travel in each direction with medians, berms, long entrance and exit ramps, banked curves and separated grade crossings. In order to get the project completed in 20 months, 1,100 engineers were employed.

Ÿ Near Everett, designers first considered a tunnel but decided instead to remove 1.1 million cubic yards of rock and earth to create the largest open cut of its time. A standard sight distance of 600 feet was chosen and straightaways were designed for 100 mph.

Ÿ Innovations included laying out the route to take advantage of southern exposures to help allow the sun to melt ice and snow. In those original 160 miles, there were more than 300 bridges and culverts, nine interchanges, 10 service plazas and 11 tollbooths.

Ÿ Once designs were completed, 155 construction companies and 15,000 workers from 18 states went to work. Within a year the road was being constructed at a rate of 3 1/2 miles per day. The turnpike entered service Oct. 1, 1940, reducing travel time between Pittsburgh and Harrisburg by three hours.

Ÿ Ironically, due to World War II, automobile production stopped from 1942-46. Still, early actual usage was 2.4 million vehicles per year.

Ÿ Today the original 160-mile route has been expanded to 514 miles, carrying 156.2 million vehicles per year.

Ÿ Speed limits have been regularly adjusted: In 1941, 70 for cars and 50-65 for trucks.

During World War II a national speed limit of 35 mph; post war the speed limit returned to 70 mph.

In 1956 the speed limit was reduced to 65 for cars, buses and motorcycles, all others 50.

In 1974 the National Maximum Speed Law reduced the turnpike speed to 50.

In 1995 it was raised to 65 except for areas where the population was greater than 50,000; in 2005 it was raised to 65 except for tunnels, toll plazas and the curved portion near the Allegheny tunnel.