Triangle warning signs were obligatory for all car owners in case of breakdown but now they're not, as the DGT considers them obsolete.
Those warning triangles came into use in 1999 but since then there are much more advanced systems for warning fellow road users that you’ve broken down and are obstructing the road.
Such an example is the V16 Autonomous Emergency Signalling device which is approved by the DGT (Dirección General de Tráfico).
Consequently, the reflector triange is being phased out so that by the 1st of January 2026, you will have to have had them replaced by a DGT-approved device. As mentioned above, the V-16s were approved for use in July 2021 (Real Decreto 159/202).
Apart from emitting a flashing orange light to warn other traffic, some models of the V-16 beacon may also have geolocation features built-in and Bluetooth technology, which will allow users to connect them to a mobile so they will be able to send a request for roadside assistance when it is activated.
The reason that this change came about was that quite a few drivers have been knocked down when getting out of the vehicle in order to place the triangles.
(News: Spain)

AHH. Reread your previous. Gotcha now. But you’re correct. How will you warn others. ??
Hence I carry two warning triangles.
But on a bend. I’m sorry. I miss your point. Unless it’s a one track road. Or a confused English driver on the wrong side. ??
Patrick: the thing that strikes me is that if you’ve broken down and behind you there is a bend, you’re supposed to put the triange before the bend to give warning to approaching drivers… having an orange beacon on your roof is going to avert a nasty surprise there, is it?
Hmm. As opposed to driver’s getting out of the vehicle to find the new beacon in the boot of the car. AHH there it is. Beside the warning triangle. !!
Personally I carry two warning triangles and this beacon thing. Belt and braces. !!