Zebra crossings are easy to spot

By now, your new school term would have started and you would be commuting to school once again. When you are travelling on the road, whether on foot or by a vehicle, you have to be extremely careful and obey all the road rules properly.

Do you know these road rules? Even if you don't know them all, it's very important that you know and understand the rules and road signs that are applicable to pedestrians.

When it comes to pedestrian road signs, one of the most important and familiar signs are the zebra crossings.

These markings, which help you to cross the road, are the longitudinal lines which run parallel to the flow of traffic. Between 40 and 60 cm wide, these lines are alternately in a light colour such as white or yellow and black (they are left bare if the road is black). Pedestrians always have the right of way on these lines, but this may not always be the case in countries such as Sri Lanka.

In places like the UK though, these rules are still widely applied. UK was also the place of birth of the zebra crossings. And much like the English language, it has been used all over the world without any copyrights or payments. They were first used in over a 1,000 sites in the country in 1949. The original form was stripes in blue and yellow.

Before their introduction, belisha beacons (black and white poles topped by flashing amber globes were used; these were introduced in 1934 by Minister of Transport, Leslie Hore-Belisha, who also re-wrote the Highway Code) and parallel rows of studs were used as road crossings. Zebra crossings were introduced for better visibility; they were introduced into the law in 1951.

In the UK, these crossings are marked by belisha beacons on both sides of the road. Another road signal that is very much in use even in our own island is the pelican (Pedestrain Light Controlled) crossing. This uses lights to control the traffic flow while an icon of a red/green man is illuminated for pedestrians to cross. These were introduced in 1969 and were intially known as panda crossings.

Other such systems used in different parts of the world are puffin, toucan and pegasus crossings. Suggestions have been made recently in some countries to modernise the appearance of zebra crossings to real zebra-like curved lines.

These proposals have not received approval, both due to aesthetic and safety reasons. The success of the crossings is partly due to their most effective design, which is easily recognisable at any place.

Can storms be prevented?

Of late, the world has been experiencing natural disasters in the way of hurricanes, storms and ice storms. It seems strange that despite advancements made in science and technology, mankind is still vulnerable to natural disasters.

It had been queried some time ago whether it is possible to stop a hurricane if spotted on satellite early, by dropping tonnes of dry ice, liquid nitrogen or silver iodide crystals onto it and making the hurricane dissipate(dissolve). Even a project was carried out in this regard. Let's inquire into the background of this project.

The success of using silver iodide for cloud-seeding and to increase the amount of precipitation (water vapour) in small clouds led to the big interest in scientific weather control in the fifties. This spawned Project Stormfury where, from 1961 to 1980, U.S. scientists conducted extensive research into the possibility of weakening hurricanes with cloud-seeding techniques.

The assumption was that it might be possible to seed the first rain band outside the wall of clouds around the storm's eye.

The seeding would cause super-cooled water to turn into ice, which releases heat. That heat would cause the clouds to grow faster, pulling in air that would otherwise reach the wall of clouds around the eye.

With its supply of air cut off, the original eye wall would fade away, and a second would grow outside the first. Because the new wall would be wider than the original, the air spiralling into it would be slower, and the hurricane would have less power.

Results were inconclusive(not definite) and the expensive experiment was abandoned in 1980. It was also realised that even if proven effective, there was no practical way to decide when, where and which storms to attack. More recently, speculation has surrounded a substance called Dyn-O-Gel, a powder that absorbs large amounts of moisture and then becomes a gooey gel.

It has been successfully used to dissipate small clouds. However, scientists have estimated that it would require more than 37,000 tonnes of the stuff to dissipate a hurricane.

Finally, it should be remembered that hurricanes, along with other storms and ocean currents, help balance the Earth's heat.Trying to influence the behaviour of hurricanes could have consequences no one intended.

Rather than attempting to prevent storms, money should be diverted to enabling better forecasting and building suitable flood defences.