Many cars these days have automated stop-start, mine doesn't so I do it manually, if I am sitting at red lights and they change to green then I start my engine and go, I don't wait at the green light for 20 seconds before moving, time from turning the key to moving is sub-1 second, I don't start the engine, then put it into gear, then go, I park with it in gear and ready to go, I can easily be at any speed limit within 20 seconds.
Maybe in the USA, you do not need to turn your engine off at red lights, but in other countries it is a legal requirement, including the UK.
In the UK, Rule 123 of our highway code says:
The driver and the environment. You MUST NOT leave a parked vehicle unattended with the engine running or leave a vehicle engine running unnecessarily while that vehicle is stationary on a public road.
It just wouldn’t be you Nigel without some sort of disparaging remark or swipe at the USA combined with your usual sanctimonious attitude. As always you have your complete ignorance of the United States on full display when making these condescending comparisons to the UK. Thank God I don’t live in a rigid society like the United Kingdom where government dictates and surveils every facet of everyday human behavior.
We certainly do have laws and regulations designed to eliminate air pollution, cut down on greenhouse gases and increase fuel economy such as the Clean Air Act, CAFE standards legislation (Corporate Average Fuel Economy) and newer EPA regulations governing federal greenhouse gas emissions standards for passenger cars, light trucks and aircraft.
We also have regulations and
voluntary guidelines for shutting off your engine when your vehicle would be otherwise idling such as when:
Waiting for your drive-through order.
Waiting in line at a gas station or car wash.
Dropping someone off or picking them up (e.g. at school, airport or train station).
Waiting at a railway crossing (or red traffic light in certain location dependent scenarios).
Delivery vehicles dropping off packages.
When in grid-locked urban traffic scenarios.
Some of this comes under Federal regulation and some is mandated by state law. Some is recommended action.
Depending upon where you happen to live in the United States one would have to stop and restart their vehicle dozens of times during an average trip across a city or large town and having thousands of cars turning off their ignitions at every traffic light would create havoc and it is simply not practical. As always when you compare the UK to the US you ignore the fact that we are an enormous country with a population of nearly 338,000,00 people with approximately 280,000,000 registered personal and commercial vehicles of various vintages. Imagine the 900,000 cars per day driven in New York City trying to keep traffic flowing smoothly with every car turning on and off their ignition at every traffic light. Signal timing cycle length in NYC falls between 45 and 120 seconds according to DOT regulations but usually closer to the low end of the scale. Pollution and greenhouse gas reduction goals in NYC are currently being addressed by encouraging the increased use of hybrid and electric vehicles (especially taxis and smaller delivery vehicles) and limiting daily traffic volumes.
Repeatedly stopping and starting will probably wear out your starter and use up any savings you may have gained on fuel costs in the long run. If you have a traditional car or truck you want to avoid constantly turning off and restarting your engine at every traffic light.
Cars with stop/start technology on the other hand come equipped with starters that can handle this and they have specially designed ignition systems and batteries that are also up to the task. Cars with auto start-stop will always have upgraded batteries (often marketed as 'start-stop' batteries) and a more powerful starter motor, often 'tandem solenoid' versions which cope better in the scenario where the engine has started to shut down but is still spinning, and the driver wishes to accelerate again.
Of course, if you live in a cold climate northern New England or other northern US locations in the wintertime when it’s bitter cold out you want to keep the car running so you can use your heater without turning it off in sub zero weather.
Additionally, turning your car on and off in stop-and-go traffic is not recommended because driving safely means being able to respond quickly to traffic conditions.