and a roughly similar street grid (it begins to degrade outside the city) continue beyond the city limits into Upper Darby Township, into which Market Street runs uninterrupted to 69th street at the El terminal, where it turns into West Chester Pike and runs through Delaware County and into Chester County. With the exception of Market Street, these streets can be regarded as being "named after" the streets in West Philadelphia, not continuations, as they are cut off by the park. The numbering pattern is mixed; someone traveling along Market Street into Upper Darby would cross 62nd Street, then Cobbs Creek Parkway/63rd St, then several named streets until finally arriving at 69th Street, skipping 64–68. Other major thoroughfares include Chestnut and Walnut Streets, which together form Pennsylvania Route 3. Every day, thousands of vehicles travel this route, which is one of the major commuter routes into and out of Philadelphia from Delaware and Chester Counties. In the 1960s and 1970s, illuminated signs announced what speed to drive to travel 4.3 miles into Center City without stopping for a red light. The streets were once lined with American Chestnut and walnut trees that touched across the five lanes of roadway, but many were removed due to Chestnut blight and replaced with a mix of sycamore and poplar trees. City officials found these species much more tolerant of the urban environment and resistant to disease. A handful of chestnut trees remain near Cobbs Creek. Lancaster Avenue begins at 34th street near Drexel University; runs westward to the city line at City Avenue; and continues on as U.S. Route 30 to Lancaster, York, Pittsburgh. and the West Virginia border. One of the major retail strips in West Philadelphia, it is lined with shops and restaurants through to 64th Street in the Wynnefield neighborhood. In addition, one of Philadelphia's six streetcar lines, the Route 10 Green Line, transports commuters and students daily along Lancaster Avenue from 36th and Ludlow streets to 63rd and Malvern Avenue in Wynnefield. Crime The intersection of 52nd Street and Market Street in West Philadelphia was listed number eight in a 2007 list of the city's top ten recreational drug corners according to an article by Philadelphia Weekly reporter Steve Volk. The Philadelphia Police Department divides West Philadelphia into four patrol districts: the 16th, 18th, 19th, and 92nd. Schools Primary and secondary schools Public schools The area's public schools are