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Can-Am Spyder roadster

Q Are there limits on vehicle size when lane-splitting? I had a Can-Am Spyder splitting lanes next to me during my morning commute on Highway 4 near Willow Pass Road. The overall width on the Can-Am Spyder is almost five feet. Maybe I should experiment lane splitting in my 3/4-ton 4x4?

Adam Jensen

Walnut Creek

A There are no limits on the size of a vehicle that it is legally lane-splitting. The size is limited solely by the size of the lane. Technically, any vehicle can share a lane with another vehicle in California.

Added Mark-the-CHP-Man: "For an example of this, go to any good-size intersection which does not have a marked right-turn lane. When the light turns red and traffic backs up, if there is enough room, you will see cars of all shapes and sizes splitting the right lane up to the intersection where they then make a legal right turn on red. However, if a vehicle straddles a painted lane dividing line, as I suspect the Can-Am was in the scenario cited by Adam, the operator is in violation of 21658(a) of the California Vehicle Code."

Q So ticketing trucks on Interstate 880 near the Port of Oakland is a tough task. And that's a reason to not do it? If the police can't, get new police. It would not make the slow commute even tougher, except temporarily. Once truckers knew they had to obey, it would make the commute for cars better.

Fire the cops giving lame excuses.

Tom Day

Sunnyvale

A Lame excuses? I think not. Drive 880 during the commute and imagine a CHP cruiser pulling over a big rig along the shoulder on one of the East Bay's most congested roads. If a police cruiser parked along the Dumbarton can bring that commute to a crawl, a ticket stop on I-880 could lead to even greater backups there.

Q Every time I go through the Caldecott Tunnel, I wonder where they took the dirt when excavating the fourth bore. Would you let me know so that I can tell my family?

Heidi Alef

A There were an estimated 210,000 cubic meters of dirt excavated from the East Bay hills during the fourth bore dig, and most of the dirt was taken to Treasure Island, which was formed by Bay dredgings in 1936 and '37. A small percentage had evidence of elevated levels of naturally occurring hydrocarbons and was taken to Keller Canyon Landfill in Pittsburg.

Q I'm sure you'll get multiple emails on your story about congestion on the Dumbarton Bridge. While I'm sure your Caltrans contact is correct at the macro level about the effect of the Facebook campus, the traffic flow had improved over the last couple of months until last week, when things suddenly changed for the worse again. Something other than Facebook has happened recently. I believe the empty Menlo Park police cruiser parked near the bridge has had a negative effect. ... Unless I've been hallucinating daily for the last year, the Facebook campus has been open longer than a week. I'm not buying the Caltrans engineer's weak-sauce explanation for why Dumbarton traffic was at a standstill just past the toll plaza last week. ... Why was the police car parked along the bridge? I am convinced its presence was the problem for added delays of recent days.

Greg Heibel, Craig Miller, Matt Smith and more

A I'm convinced you are spot on. This was an attempt by Menlo Park police to curb speeding in the area by parking one of their patrol cars near the bridge. The cop car has been moved, and some drivers are already reporting that the commute has eased.

Q Gary, 'fess up. When you are driving on Interstate 280 to San Francisco, how fast are you traveling? Are you going 65 mph, which is the speed limit there? I bet not. I bet you are going as fast as the rest of us -- 75 to 85 mph. So why isn't the 65-mph limit at least 70, as it is on Interstate 5?

Michael Garcia

Sunnyvale

A OK, I'm 'fessing up. When I'm behind the wheel on 280, I have been know to clip along at 70-plus, which usually leaves me in the slow lane. But the speed limit won't be raised to 70 mph. Caltrans can set a speed limit of 70 mph, but after consulting with the California Highway Patrol, and upon the basis of an engineering and traffic survey, the state says it has no plans to raise the limit to 70.

Said Roland-the-Caltrans-Speed-Man: "Part of Route 280 seems to be rural, but it is a major commute route between San Francisco and San Jose. It runs through many cities with many interchanges in between. During peak periods, the mainline traffic may experience slowdown due to heavy volume coming from an onramp and traffic exiting to an offramp."

So 65 mph it remains. And I'll slow down when the doctor gives me a green light to begin driving again.

Follow Gary Richards at Twitter.com/mrroadshow, look for him at Facebook.com/mr.roadshow or contact him at mrroadshow@mercurynews.com or 408-920-5335.