Q When I drive Interstate 680 from San Jose to just past Durham Road in Fremont, the northbound and southbound lanes split apart.

There is a big hill between the lanes and I can't decide if it was done that way on purpose, or if it is an unfinished ramp or something like that. Do you know?

Dana Smith

Campbell

A Sure do. In the 1960s when that portion of I-680 was built, construction began on a freeway-to-freeway overcrossing over southbound I-680 north of Durham as part of a plan for an interchange connecting I-680 with a future Route 238 alignment. But those plans were scrapped in the 1970s during Jerry Brown's first stint as governor and that section of 238 wasn't completed.

2000: The unused overpass, which was later demolished.
2000: The unused overpass, which was later demolished. (Bay Area News Group)

Between 2001 and 2002, when Caltrans built the interim southbound I-680 carpool lanes, the unfinished overcrossing was demolished because it was no longer needed nor up to code.

Q Can you find out when Caltrans intends to finish the Tunnel Road onramp to east Highway 24 just before the Caldecott Tunnel? This has been blocked with K-rail for so many years I can't remember, and it's a difficult, dangerous, short merge, with short sightlines, speeders in the right lane and a horrible concrete curb on the left of the ramp that makes it even harder to merge safely. It really sucks!

And now that there are no tunnel closures anymore, drivers come zooming up that right lane and nearly force you into the K-rail as they fly by while you're trying to merge.

Linda Landau

Orinda

A Caltrans will finish this any day now. The state will then move the K-rail to work in the median.

Q During the construction of the 680/580 interchange a few years ago, new metering lights and warning signals were installed on the flyovers for both northbound and southbound 680 to eastbound 580. Yet no matter how bad the traffic is on east 580, I never see them turned on.

Is there a legitimate traffic engineering reason behind this, or did somebody just forget they were there?

Ken Willson

Dublin

A Three years ago Caltrans had a plan to turn on these meters, but cities in the area worried that drivers trying to bypass the metering lights would jam their streets. Nothing has changed.

Q Driving north on Interstate 280 at evening rush hour, I noticed a white Audi with lots of equipment on the roof. It was in the fast lane, and when it passed me, I recognized all the signage on it -- it's the Stanford autonomous car.

When that's on the public road, is the human at the controls, or the computer?

Roland Dumas

A Both. The driver must be seated in the driver's seat, monitoring the safe operation of the autonomous vehicle, and capable of taking over in case of a technology failure or other emergency. New regulations are being considered and must be in place by 2015. Audi says it may take a decade for self-driving cars to enter production.

Look for Gary Richards at Facebook.com/mr.roadshow, follow him at Twitter.com/mrroadshow or contact him at mrroadshow@mercurynews.com.