With its landscaped embankments, limited access, and depressed roadway, Arroyo Seco Parkway (now known as the Pasadena Freeway) became the prototype of the Los Angeles freeway system. Motorists enjoy a scenic drive featuring landscaped embankments lush with native chaparral. The curving alignment traverses a chain of small parks shaded by sycamores and eucalyptus and exposed views of the snow-capped San Gabriel Mountains. The experience gained by observing traffic operations on the parkway confirmed the value of acceleration/deceleration lanes and the minimum practical width for planted medians. The prohibition of cross-traffic provided additional driving safety and convenience. Facts 1. This 6.7-mile-long parkway was the first urban freeway to be built in the United States west of the Mississippi River. 2. Asphalt and portland cement concrete pavements were installed side-by-side for comparison purposes. 3. Despite having to carry over four times its projected design-year traffic, the parkway has remained in almost the same configuration as when it was opened in 1940.