Okay. I'll state the obvious first. The way to reduce traffic is to get people out of their cars and walking/cycling/car sharing/using public transport instead.
That's the obvious fact.
How you do that is another matter. But first you need to understand why people are using their cars. Where are they going? Are there alternatives? If there are, why are they not using the alternatives?
This in itself is not straightforward, but let's take an example that is easier than most. Weekdays the car parks at or near Marple station are usually full. Where have those cars come from?
I can see some possibles. They could have come from Mellor. Or Compstall. Or Chisworth/Charleworth. Or from New Mills.
New Mills has two railway stations. But I've heard it said that people drive to New Mills to get the train from Marple. Why would they do this? Well a peak time return to Manchester is £10.70, compared to £6.80 from Marple. That's a HUGE difference to go one stop on a five minute journey. With free parking, it's a no-brainer to drive to Marple or Rose Hill from the New Mills area. Hey, it's £8.20 from Strines to Manchester. The train fares are offering a massive encouragement for people to drive to the station in Marple, rather than potentially drive/walk/cycle to a closer one. How many people are actually doing this, I don't know. But if you could quantify it, you could see the impact on traffic. And even a few people doing it will add to the traffic problems.
If you lived in Mellor and wanted to get to the train you could get the hourly 375 bus to the station. But the bus doesn't connect well with the trains. If you wanted to get to Manchester, you could end up with a 15-20 minute wait at the station to change. Or longer. So what are you going to do? Drive probably.
Just trying to tackle the problems at the stations open up whole cans of worms that are difficult to solve. To get people from Mellor to the station you need more buses. To get people to use New Mills instead of Marple, you need to reduce the financial incentives to use Marple. That's either change the fares, or charge for parking. And if you charge for parking, you then need to make most of the streets near the stations permit parking only else people will just park on the road.
I genuinely don't think there's any quick fixes on this. Everything simple that can be done is basically a sticking plaster. You need to get people out of their cars, and to do that you need a lot of changes to be made.
(For the record, I mostly work from home so have no commute. When I do go to one of my employer's offices, I travel by train or bus. I have a car. It sits on the drive most of the time. During the week I usually only drive to swimming pools in the evening - Avondale or Hazel Grove usually. Neither can be easily reached by bus. At weekend the car gets more use. It might go to visit parents in Tameside. Or to go shopping. Or further afield. At weekend I tend to go swimming in Romiley. If the weather is good, I cycle. I used to live in London and did not own a car. I would be really happy if I didn't own one now..)