They’d agreed not to fight when the city was being built. It was an equable arrangement. The traffic lights ruled the roost in the city centre; the roundabouts kept things moving elsewhere on the grid roads. All was well for fifty-five years but then…

The roundabout at the top of Brickhill Street caught wind of a plan to replace it with lights. Quite how it obtained this knowledge no one could say, but grapevines exist everywhere, even amongst traffic networks.

‘Outrageous,’ it shrieked. ‘Don’t they know how important I am?’

The lights on Wolverton Road preened with pride. Recently installed to serve a new estate, they knew nothing of the decades-old agreement.

‘Important?’ they sniffed. ‘You’re only a bush-covered circle in the middle of the road. We’re the important ones. Look how colourful we are.’

‘You make people stop when there’s only one car,’ protested the roundabout. ‘You should’ve been a mini roundabout!’

‘Yes, but…’

‘And you need electricity and programming.’

‘True, but…’

‘And sometimes you break down! We keep the traffic flowing freely. Not only that but I’m home to a family of foxes.’

‘OK. OK! Enough with your boasting. It’s not like we can do anything to help.’

‘But you can,’ said the roundabout. ‘You’re connected to the traffic control system. If you can receive messages, you must be able to send them.’

‘Hmmm, perhaps. But why should we help?’

‘Because we had an agreement. And if you don’t…well, we’ll find a way to get you replaced! We are more than mere circles!’

The lights sighed. ‘Very well. We’ll see what we can do.’

*

The following morning, Milton Keynes’ roads were gridlocked. Every set of lights across the city was flashing in a most unusual pattern. And no matter what the city engineers tried, they couldn’t reset the system.

‘Could it be some kind of code?’ Professor Miriam Lewis asked, when she eventually arrived at work. She’d abandoned her car and walked two miles to her office at Bletchley Park, historic home of the WWII code breakers.

‘Who would use traffic lights to send a message?’ asked Doctor Russell Smith. He’d cycled to work.

Professor Lewis shrugged. ‘I don’t know, but we might as well attempt to decode it. No one is getting any other work done today – the city is at a standstill.’

It took an AI program only two hours to decipher the code. Professor Lewis called James McKenney, head of traffic control, to break the news.

‘The lights want to save a roundabout from being replaced,’ she said. ‘Apparently our lights and roundabouts have an ancient agreement about who operates where. If you refuse, they will continue to disrupt the traffic flow.’

McKenney sighed. ‘I told the planners not to mess with the roundabouts. This is no ordinary city and our roundabouts are no ordinary structures. Can you tell the lights we agree to their demand?’

Professor Lewis smiled.

‘My AI system has a message ready to send.’