Q You recently printed a comment from Glenn Nelson that he was pleased to be improving his gas mileage on his commute. Glenn noted that his average mileage was 30 to 32 mpg at 65 mph, but improved to 37 to 39 mpg at 55 mph. I'm quite surprised that pleases Glenn.

Jacob Butcher

Oakland

A Why is that?

Q Consider the difference for a journey of 357 miles. Driving at 55 mph will take exactly one hour longer than driving at 65. A difference in mileage of 38 mpg rather than 31 mpg will save 2-plus gallons of gas. At $4 a gallon, that's a savings of $8.50 for an hour's effort. That's just barely over the minimum wage! I suggest that many people, myself included, would much rather spend the extra $8.50 and save the hour. I would have liked to see a discussion from you on the trade-off involved.

Jacob Butcher

A Sure, there is a trade-off for long drives. Would I go 55 to 60 mph on Interstate 5 to Los Angeles and add an hour to the trip? No. Would I travel that speed on Highway 1 from Santa Cruz to Monterey, as Glenn does? Sure.

Q I am interested in replacing my 12-year-old car with a hybrid. I know you love your Prius, but when I drove a friend's Prius, I really didn't like the way the rear window design reduced my visual field. I couldn't see anything behind the car for a good 12 to 15 feet. So what other hybrids are out there that have been tested and approved by your readers?

Teri Lockhart

Sunnyvale


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A The Ford Fusion hybrid gets a lot of love, but there are 30 or so hybrids on the market. I'm sure others have their favorites and will let us know.

Q I have a question that I can't find the answer to anywhere, but am certain you will know. On Highway 24 approaching the Caldecott Tunnel from either direction, there are temporary lane markers that are placed in different spots, depending on traffic and time of day, that can, for example, merge three lanes into two.

These markers are orange plastic sticks that appear to be temporary, and look like they are stuck into placeholders in the pavement. I always assume that Caltrans workers must manually install them, since they look so temporary.

But my nephew claims these are installed remotely, that they are actually under the road and Caltrans simply indicates when they want them to be raised remotely and electronically into place. I think he's making that up. Do you happen to know?

Jennifer Spoon

San Ramon

A The kid knows what he is talking about. At any given time at the Caldecott Tunnel, depending on traffic demands, four lanes are merging to two lanes in the eastbound or westbound directions. Caltrans uses pop-up delineators to gradually close lanes of traffic from four lanes to two lanes. The pop-ups are so named because they are air-controlled and pop up from the ground. Maintenance crews use a remote control system to raise or lower the pop-ups.

Once the Caldecott fourth bore project is completed in late 2013, the state will no longer be reversing the direction of the center bore, and the pop-ups will become a part of California transportation history.

Q Over the past few weeks there has been an odd construction project on Woodside-La Honda Road from Tripp Road in Woodside to Pescadero Creek Road in La Honda. First, the reflectors were removed. Now, the asphalt in the center of the road is being removed. I'm hoping this new asphalt will eventually be turned into a rumble strip similar to what was done on La Honda Road west of town to San Gregorio some time ago. What can you tell us?

Edwin Hering

La Honda

A That's exactly what will happen. Caltrans will install median rumble strips here to reduce the severity of head-on collisions. This strategy has also been tried on Highway 25 west of Hollister, on Vasco Road in the East Bay and on sections of Highway 1 with tremendous success.

Q You made a recent reference to the new merging lanes that are going to be added to Interstate 680 between Sycamore Valley Road and Crow Canyon Road. Please explain to me what "merging lanes" are. I must be dense. How do they differ from current onramps, or am I really confused?

Doug Emig

Danville

A Technically, you are not dense. Merging lanes are short ramps feeding traffic onto or off a freeway. Auxiliary lanes like those coming in Contra Costa County run from one interchange to another, but are often called merging lanes, as well.

Q I commute to and from Foster City and the East Bay every day via the San Mateo Bridge and have a radar detector in my vehicle. Every day the same phenomenon occurs. While westbound in the morning, the radar detector will go off when I get on the high-rise (X band if that means anything to you). Yet on the few times I have seen a CHP on the west end, their radar sets off a different type (K band).

Also, in the afternoon while eastbound, the laser warning goes off in the same portion of the bridge. Yet again, no CHP. So that got me to wondering. Is this something related to air traffic inbound to SFO?

Jeffrey Yahoe

A Most likely. Airport officials say there is a nondirectional beacon just offshore of Foster City south of the San Mateo Bridge. It most likely doesn't cause any problems with the radar detector because it broadcasts at 379 kHz, which is just below commercial AM radio. Best guess: It may be the weather radar on aircraft flying in and out of SFO.

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