Came across this subject on another forum that I felt worth sharing.
I, like many others, slow down using engine braking and gearing when approaching a stop or other situations requiring slowing down. I'll generally not apply my brakes unless/until necessary. In doing so, there is no indication or warning to whoever is behind me that I am slowing down. If they're not paying attention and notice my speed change, which can be fairly rapid, I'm putting myself in danger of being rear ended. As a precaution I am now going to start activating my brake lights while I'm gearing down and engine braking. I think this is a good "preventative" practice, one that I've not heard anyone mention before nor have I thought about it before. Something I do do is when stopped and there's traffic approaching from behind, I'll flash my brakes a few times just to ensure I'm getting their attention that I'm stopped or for that matter, that I'm actually there.