Southbound on Interstate 280 near Magdalena Avenue during a January 2010 rainstorm.
Q I really appreciate the articles you publish that go into the history and technical reasoning behind why our roads were designed the way they are. If I’m going to suffer through traffic because of a design decision, it helps me mentally to know why.
That being said, I am really curious why some bottlenecks were apparently artificially created along south Interstate 280 through Los Altos and Palo Alto. These bottlenecks all involve the freeway narrowing from four to three lanes, only to widen again just shortly after.
Two of them are next to the Page Mill Road exit. On southbound I-280, the fourth lane is lost when it becomes the offramp to Page Mill. It is soon reintroduced as the onramp for cars coming from Page Mill but the freeway doesn’t widen back to four lanes until you hit the carpool lane on Magdalena Avenue. Is this a way to give cars entering 280 a dedicated ramp that is not shared with the rest of the interstate?
A The lane changes at the Page Mill ramps are to make merging and exiting the freeway easier and ease backups in the slow lane. But that’s not the biggest issue on this section of 280.
Q I want to motivate this last one by saying I have a way to improve the Highway 101 southbound slog through Palo Alto and Mountain View in the afternoon. If we added a fourth lane before the infamous Magdalena bottleneck on 280, many more drivers (myself included), would take 280 back home instead of adding to the 101 nightmare. The net result is an improvement in both the 280 and 101 commutes. What is the cost? It looks like a brush and bucket of paint would be required to add that lane. The road already seems paved and there is plenty of room for the fourth lane at Magdalena. Any idea why it was designed this way?
A Not sure what the cost would be, as no studies are current. But a Caltrans source told me two decades ago that the lane drop was approved when the carpool lane was added at Magdalena on south 280, forcing solo drivers to merge right and not get trapped in the carpool lane unknowingly.
Q Why won’t the county synchronize the lights on Page Mill Road as they have on Lawrence Expressway? You would think the main artery for the Stanford Industrial Park, birthplace of Silicon Valley, would have this old technology in place.
A They are coordinated during the morning and afternoon commutes. But since Page Mill has two lanes only in each direction it reaches capacity very quickly and any small issues like stalled vehicles or accidents could mess up the timing system.
When Page Mill changes to Oregon Expressway east of El Camino Real, there are problems. Oregon is under construction, and many loop detectors in the pavement have been taken out. Once work ends in a couple of months, the signals should work much better.