4 . When you walk on a sandy beach, it takes more energy than walking down a sidewalk, because the weight of your body pushes into the sand. It turns out that the same thing is true for vehicles driving on roads.

"The weight of the vehicles creates a very shallow indentation（凹陷）in the pavement, and it makes it such that it's continuously driving up a very shallow hill," said Jeremy Gregory, a scientist at MIT. He modeled with his teammates how much energy could be saved, and greenhouse gases avoided, by simply hardening the nation's roads and highways.

And they found that hardening 10 percent of the nation's roads every year could prevent emissions equal to 440 megatons of carbon dioxide over the next 5 decades—that amount is equal to how much CO2 you'd spare the planet by keeping a billion barrels of oil in the ground or by growing 7 billion trees for a decade. It reduces 0.5% of projected transportation emissions over that time period.

As for how to harden roads, Gregory says you could combine small amounts of certain fiber with high technology into paving materials. Or you could pave with specially-made concrete, which is harder than ordinary construction materials.

This system could also be a way to shave carbon emissions without some of the usual barriers. "Usually, when it comes to reducing emissions in the transportation department, you're talking about changing policies related to vehicles and also driver behavior, which involves millions and millions of people---as opposed to changing the way we design and preserve our pavements. That's just on the order of thousands of people who are working in transportation agencies." And when it comes to improving our streets and highways, those agencies are where you might say the rubber meets the road.

5 . North American Train Routes for a Family Vacation

The Adirondack

Considered one of the top ten scenic train rides in the world, the Adirondack train route travels from New York City's Penn Station to Montreal, Canada. The trip is great for a weekend away in either Montreal or Manhattan. The route will take you past West Point Academy, the Hudson River Valley and fifty miles of Lake Champlain.

The Vermonter

The trip from Washington, D. C. to St. Albans, Vermont, takes you from the U.S. capital, through the beautiful New England states of Connecticut and Massachusetts on the way to Vermont. As you travel through New England towns, you'll be able to see some of the most beautiful scenery in this area, including rivers, falls and covered bridges.

The Downeaster

The Downeaster was established in 2001 and was expanded several years ago northward to Freeport and Brunswick, Maine. The short ride (between three and four hours) includes a trip along the beautiful Maine coastline. With five round-trips offered each day, this route is a great way for Massachusetts families to visit Maine for a day or longer. Many of these routes carry volunteers to aid passengers with questions about local attractions and destinations.

The Pennsylvanian

Both New York City and Pittsburgh are great family vacation destinations and the Pennsylvanian route takes you through the beautiful Pennsylvanian landscape between the two major cities. The 9.5-half hour trip travels through a variety of different terrains(地形), and stops along the way including Newark, Philadelphia, Harrisburg and Altoona. The connecting train service is available for those looking to travel to Cleveland, Chicago, and Toledo from Pittsburgh.

7 . Forget Cyclists, Pedestrians are Real Danger

We are having a debate about this topic. Here are some letters from our readers.

★Yes, many cyclists behave dangerously. Many drivers are disrespectful of cyclists. But pedestrians are probably the worst offenders.

People of all ages happily walk along the pavement with eyes and hands glued to the mobile phone, quite unaware of what is going on around them. They may even do the same thing while crossing a road at a pedestrian crossing or elsewhere. The rest of us have to evade（避让）them or just stand still to wait for the unavoidable collision（碰撞）.

The real problem is that some pedestrians seem to be, at least for the moment, in worlds of their own that are, to them, much more important than the welfare of others.

——Michael Horan

★I love the letter from Bob Brooks about cyclists（Viewpoints, May 29）. I am afraid they seem to think they own the roads.

I was walking across Altrincham Road one morning when a cyclist went round me and on being asked what he was doing he shouted at me.

The government built a cycle lane on the road but it is hardly used.

The police do nothing. What a laugh they are!

The cyclists should all have to be made to use the cycle lanes and wear helmets, fluorescent（发荧光的）jacket and lights at night and in the morning they should pay some sort of tax and be fined for not wearing them.

——Carol Harvey

★Cyclists jump on and off pavements（which are meant for pedestrians）, ride at speed alone the pavement, and think they have a special right to go through traffic lights when they are on red.

I was almost knocked down recently by a cyclist riding on the pavement when there was a cycle lane right next to him.

Other road users, including horse riders, manage to obey the rules so why not cyclists?

It's about time they had to be registered and insured, so when they do hi a pedestrian or a vehicle, or cause an accident, at least they can be treated and there might be an opportunity to claim compensation.

——JML

Write to Viewpoints of the newspaper.

Car registration plates (牌照) are just a series of numbers and letters, right? Well, yes…but not for everyone.

France was the first country     1    (introduce) plates in 1893. Early number plates differed     2    shape and size, and were made of lots of different materials, including iron, cardboard and even pressed soybeans. In fact, it was not until 1957     3    car manufacturers and the governments agreed on standardized(标准化) plates.     4    was first registered in the UK was A1. The letter “A” showed the number was from London, while the number “1” showed it was the first number issued. At the moment, number plates     5     (consist) of a sequence of letters and numbers are applied in the UK.

Different EU countries also use different arrangements of numbers and letters, and     6     systems have changed many times because these letter-number     7     (combine) keep running out. In the past decades, some number plates     8     (become) extremely valuable, particularly those that spell out words.     9     (basic), numbers on the plates can be used to represent words or parts of words. For example, “NVERLA8” means “Never Late”. And the most     10     (expense) number ever was “M1” which an anonymous(匿名的) buyer has acquired for ￡331,000.