The trick about effectively stopping traffic is to use traffic to stop traffic and then you can go off and stop traffic elsewhere. This also prevents motorists assaulting protestors stopping traffic, sometimes using their vehicles.
These are only suggestions: you are responsible for your actions and relative safety. The actions suggested here are very probably illegal.
These suggestions are to ensure that there is no more business as usual while governments fail to properly address the climate crisis.
Traffic lights: Traffic lights can be used to stop traffic. The Great Train robbers used a battery to light the red train traffic light so that the train stopped. No need to do that – just smash them.
A good lump hammer and a length of metal rod will do it. Make sure that you wear eye protection from smashing glass – or at least turn your head away – and thick gloves to protect from electric shock. Make sure that you can reach the lights – maybe take some small steps. It’s best that you have accomplices to prevent you from being attacked by motorists as you smash the lights.
Buses: Buses are great because they’re pretty big vehicles and they have an off switch on the outside. Turn the off switch as the bus is waiting in traffic. Be nice to the driver, he’s only doing his job and you are obstructing him. Explain why you are immobilising his bus, offer him a flapjack and suggest that he get on his radio to tell control that he is stopped. Tell him that if he goes to turn the outside switch to run again, you’ll just switch it off again. If he tries switching the outside switch to run, switch it off and open the bonnet at the back and disconnect the ignition leads. It will be hot in there so wear thick gloves.
Explain to the passengers why you have commandered their bus – a good opportunity to discuss the climate crisis.
When the next bus arrives it will need to pass the immobilised bus. There’s an off switch on the outside…
Cars: The best way to immobilise cars is to take the keys. If someone is trying to run you over, take the keys and throw them far away or down a drain.
More damaging ways – which I suggest that you avoid. Pliers or water pump pliers will rip tyre valves out. Get a good grip and pull hard. Tyre valves can be cut with a Stanley knife but you probably shouldn’t have a knife like that in public. Motorists will often drive with deflated tyres ruining their tyres. Cars can be turned on their sides or roof (immobilise by taking the keys and consider letting the occupants out first). Sharps can be used to destroy car tyres.
If you’re going to stop cars with your bodies try to get bicycles between you and the cars. Motorists are far more willing to drive into people than bicycles because bicycles might damage their cars.
30/10/21 23.45 Apologies that I assumed that the bus driver was a man. I very rarely catch buses since I am usually cycling.