The thought of sawing them by hand is keeping me awake at night.
What powered ,safe, idiot proof method can you recommend?

Chainsaw and a bucket of something to clean the tar off the chain (if they’re proper reclaimed sleepers).

Depending on what you are using them for will determine how you cut them. I have built lots of retaining walls with them and depending upon what finish I require or the accuracy of the cut I have used a circular saw or chain saw. Always check for any bits of metal or clips imbedded in the wood before you cut.

Chainsaw.. and i can highly recommend a stihl easyfile to keep it sharp

If they are reclaimed proper railway sleepers then I’d say don’t do it.

I had to help cut 30 of them once, the dust/tar was awful and the bits of lead hidden in them were a nightmare. We had 4 big chainsaws that we swapped after making one cut, each chain would be blunt after a cut so we had one person continually sharpening the chains as we cycled through the saws, we got through a few chains too due to them hitting aforementioned hidden bits of metal

Absolute nightmare, avoid at all costs

Chainsaw, good luck if you have some hardwood like Iroko or Jarrah.

Conversely, if you’re buying the green wood landscaping jobbies from wickes or the like, an extra-long jigsaw blade will be sufficient.

As above proper reclaimed sleepers are a nightmare. If they’re not covered in 100 years of highly toxic substances then a chainsaw is best, but circular saw is (slightly) more idiot proof. How big an idiot are you? 😀

I’ve just had to cut and sand some Iroko funnily enough – man that stuff is hard!!

If you really have to cut old sleepers then I recommend wearing a boiler suit and all in one face mask/goggles

Lovely wood though – I had a bit left over so made a base for my new wheel truing stand.

+1 What Houns said. Old ones should be treated as hazardous waste and shouldn’t be used. They shouldn’t be sold afaik.
You know where the loo on old trains used to drain right?
+ all of the old fuel, soot, grease, oil, squashed people etc. etc..

New ones, chainsaw, circular saw (cut from both sides), reciprocating (Sabre) saw.

Yep they really shouldn’t be sold, In hindsight I wish I refused to do them. You can see some of them here, each sleeper had to be cut to length (no we couldn’t just cut in half 🙄 ) then in half with the 45 degree angle, then routed so the signs could slip in.

Many years ago knew a chap who worked in the depot where they assemnbled points and crossings for BR, and he said cutting them was a nightmare as all sorts of stuff was ingrained into them, over the years, and when burnt they also spit out nasty contaminents, so all the offcuts went to landfill.

Also be aware of dust, get masked up, depending on where you source them – the ones I got from a reclaim yard many years ago were yellow when cut.

This turns out to be because they were Russian in origin, and had been impregnated with something foul to prevent decay/mold/whatever.

Beware the depth of your circular saw. If it gets stuck it’ll kick when you least expect it and much like a swan, it’ll break your arm. (Probably not)

Just concentrate and hold on tight.

Well this is how I did it…

They are new soft wood sleepers.

What powered ,safe, idiot proof method can you recommend?

Chainsaw

Er….. safe ??. hardly 😯

Handsaw, just make sure it’s sharp and you’ll be fine.
Some folk spend hundreds of pounds on gym memberships or go off on sporty jaunts and all you need is several sleepers and a hand saw.

Festool chainsaw

New and softwood – if you have less than say half a dozen and a decent saw I’d be tempted to do by hand – nice bit of exercise for a Saturday morning!

The OP question has been answered, but

You know where the loo on old trains used to drain right?

You know they still do that!

I did a lot recently, angled cuts and full length cuts. I started with a small circular saw and ended up with a big one. Horrible, horrible thing. One of the scariest things I’ve ever used, it felt like tickling satans balls every time I fired it up. I had a couple of bad kicks and the power was crazy. The chainsaw is a piece of cake in comparison, it doesn’t feel dangerous at all as long as you respect it. If you go circular saw then I found out that there is a lot of advice online which helped tame it a bit. Still scared me though.

Been chopping some today. Circular saw from both sides.

A slight aside but I’ve noticed East Lancs Railway (for anyone in Rossendale) are removing loads of old original wooden sleepers and replacing with modern concrete ones.

I try to always be afraid when using power cutting tools – it helps keep me sharp, if you’ll pardon the pun…!

May I suggest…..

Jamiemcf, no I didn’t. I assumed things had progressed. Glad I’m not a network rail employee.

Got a stack of last sharpen chains for cutting rubbish.

If they are modern garden supply sleepers, I know the high volume species they buy, so a plasterboard saw will probably do 😆

What is the world’s most powerful hand saw?

You know where the loo on old trains used to drain right?

As far as i am aware there are still bits and pieces that discharge straight to track. Railtracks are a weird greasy place to walk.

Rule one when we are doing bridge inspections. If you hear a train coming don’t be underneath.