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Why can a traffic jam appear without an accident?

The road clears and there is no crashed car, closed lane, or obvious reason for the queue. In a controlled experiment, drivers on a circular track developed a stop-and-go wave without a bottleneck. The cars moved forward while the congestion pattern traveled backward.

4–6 min

Questions you could explore

  • How can a pattern move in the opposite direction from the vehicles that make it?
  • Why does the spacing between cars matter?

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Cities and transport

What happens to water before it reaches the tap?

Clear-looking water and drinking water are not necessarily the same thing. In Uisce Éireann's representative surface-water process, clarification, filtration, and disinfection deal with different parts of the treatment problem.

4–5 min

What happens to water before it reaches the tap?

Cities and transport4–5 minClear-looking water and drinking water are not necessarily the same thing. In Uisce Éireann's representative surface-water process, clarification, filtration, and disinfection deal with different parts of the treatment problem.

Cities and transport

What do the two parts of an Eircode tell you?

Ireland's seven-character address code combines a routing key with a unique identifier. The operator's public example, A65 F4E2, shows how a shared first part and an individual second part do different jobs.

2–3 min

What do the two parts of an Eircode tell you?

Cities and transport2–3 minIreland's seven-character address code combines a routing key with a unique identifier. The operator's public example, A65 F4E2, shows how a shared first part and an individual second part do different jobs.

Cities and transport

How does a canal lock lift a boat without lifting machinery?

A boat inside a lock rises when the water around it rises. By filling or emptying the enclosed chamber, a conventional lock brings the boat to the level of the next stretch of canal. The gates contain the water; they do not hoist the boat.

3–5 min

How does a canal lock lift a boat without lifting machinery?

Cities and transport3–5 minA boat inside a lock rises when the water around it rises. By filling or emptying the enclosed chamber, a conventional lock brings the boat to the level of the next stretch of canal. The gates contain the water; they do not hoist the boat.

Why can a traffic jam appear without an accident? | Speech Topic | speaking.app