Dear Dr. Gridlock:

With the new $1 surcharge for paper Farecard use, Metro will drive tourists from the system. The London Underground has the same type of surcharge for tourists. Didn’t take us long to figure out it was cheaper to take a cab than ride the tube. Washington tourists will figure this out, too — very quickly.

Frank Gainer, the District

DG: The new surcharge for each use of a paper Farecard, plus the overall increase in fares, has certainly made it more expensive for tourists to get around the nation’s capital. But tourists who study up on air fares should do the same sort of comparison shopping for their short-range trips.

Those heading to London this month for the Summer Olympics face the same decisions about transit economics. The single-trip tickets for the London subway are pricey compared with other options. Visitors should look into the reduced fares they would pay after buying a Visitor Oyster card, a plastic card somewhat similar to our SmarTrip, or a Travelcard, a pass that comes in several versions, with different prices and time limits. Check the options at .

Just as friends in Britain might help you prepare for a London visit, many of you can help friends and family plan travel during their District visits this summer. Cabs might indeed be the way to go, especially for families. But look also at the cost of single trips with Metro’s paper Farecards versus the cheaper rides available to those who buy $5 SmarTrip cards.

Consider whether your guests’ Washington travels will be limited to a whirlwind day of trips to sites that aren’t within walking distance or will be spread out over a few days. If they’re packing a lot into one day, they might invest in Metro’s $14 all-day passes, but tell them to study a map and price out the separate trips to make sure they add up to more than $14.

Even with the overall fare increases, it takes a few trips at peak periods to reach $14. The investment requires even more thought if the planned travel is on a weekend. It’s off-peak, so a rider must travel more to make up the $14 investment, and it’s more difficult to travel because of the disruptions caused by Metro’s weekend maintenance program.

Merging sanely

Dear Dr. Gridlock:

The comment by D. Wood and your response [Dr. Gridlock, July 5] about drivers using merge lanes at entrance ramps to pass slower traffic reminded me of a situation I see regularly at the southern end of the Interstate 95 HOV lanes where HOV traffic returns to the main roadway, merging from the left.

Despite several lighted signs encouraging drivers to use the full length of the merge lanes, some HOV drivers weave into the main line at the earliest opportunity while, conversely, some mainline drivers tailgate dangerously to prevent merging HOV traffic from getting in front of them.

Of course, the goal should be an orderly flow of traffic, in which drivers in the left lane of the main line slow slightly and space their vehicles to allow the orderly merging of traffic. In Germany, they refer to it as the “zipper.” Such cooperation could speed everyone’s journey.

Todd Schwartz, Stafford

DG: We also call them zipper merges. They work best among drivers with some self-discipline, patience and an understanding that everyone’s trip benefits from a smooth merge. The more drivers ride one another’s bumpers for the sake of gaining a slight advantage over the motorist in the next lane, the more traffic slows for them all.

Tight spacing among vehicles forces drivers to ride their brakes. That has a ripple effect down the lane. The brake lights, and the resulting slow traffic, can extend for miles. It’s not just a question of traffic volume. Intelligent driving can ease traffic congestion.

Relative threats

This letter continues a discussion about those highway message boards that advise us to report suspected terrorism and display a 10-digit phone number to memorize while driving [Dr. Gridlock, April 26].

Dear Dr. Gridlock:

People need a reality check. The chances of causing or being involved in a crash as a result of texting with, talking on or reaching for a cellphone greatly outnumber the chances of being involved in a terrorist event.

Most of my driving attention now is committed to watching the motorists near me, as more and more are crossing into my lane despite the dividing and double yellow lines.

Patricia Meinhold, Davidsonville

DG: Those electronic messages are vague, unhelpful and are more likely to distract drivers than contribute to our safety.

But I think some other messages have their place.

Dear Dr. Gridlock:

Any idea why WMATA continues to send out the “Is that your bag?” announcement when, as far as I am concerned, it only serves to create unwanted noise?

Realistically, who would take time to go to Metro staff members about a bag left on a bench? I’ve inadvertently left a bag myself and was delighted to find it still there when I returned to the same station two hours later. Better to save announcements for something useful — and realistic.

Evelyn Wrin, the District

DG: I’m glad you got the bag back. But I don’t have the same reaction to the Metro announcements. Sure, on the one hand, this particular message has little practical effect. If there’s someone close enough to the item for you to ask, “Is that your bag?,” it’s probably not an unattended bag. But the general idea of reminding riders to be aware of their surroundings is sound. Riders are the eyes and ears of the system and the best chance of protecting it.

Of far more dubious value is the spotty program that occasionally requires people to submit to police bag inspections before they can go through the fare gates. Security experts have no idea whether this is an effective strategy. But it treats Metro’s customers as terror suspects and requires them to prove their innocence before they can ride the trains.