Darn sunrise...

I only run in the dark also. Just to scary riding in dark for me.

Sounds like the OP has developed their own perspective on riding on the road in the dark (they don't) and is instead seeking advice on splitting trainer/road rides when for whatever reason they have the time to get the whole ride done but can only be on the road part of the time. I too am very interested in gaining some perspective from others on that. It would be uncharacteristically cool if this thread didn't devolve into yet another do/don't ride in the dark debate.

I've split time indoors/outdoors for single ride sessions many times (same reason waiting for the sun to rise). I didn't change a thing about the ride goals/duration. If I had a ride scheduled for say 5-6hrs I would do as many hours, at the intensity my coach prescribed, indoors and when it was bright enough to head out I would. I could get the equivalent of a century ride in before I came in to work sometimes this spring. Worked out great for a challenging 150 mile ride I did in July.

As to your question on "is it the same as outdoors" I think the answer is most definitely yes, and likely even better so long as your intensity indoors is appropriate. Riding a traininer (again at the right intensities) is largely considered better bike training because of the consistency you can get from that type of ride.

I think that's a great idea.

Even when I do my rides completely outdoors the first 15min are warm up and very different from the rest of my ride so why not do it on the trainer. I may steal your idea :-) Do a good warm up on the trainer and the main set outdoors.

You will get as much benefit on the trainer as outdoor.

Times a million...

People already don't see bikes in the daylight...they REALLY won't see them when it's dark.

The earliest sunrise got here in TX where I live was about 0630.  So other than weekends I ride almost exclusively after work.

I used to ride at Oh-Dark-Thirty back when I was Active Duty and a big part of my riding was the commute to the ship... and having to be there and ready to go for quarters in the morning.  Lots of flashers on me, and picking the right way to work.

And I enjoyed it.

That said, I like getting out there just as I can see the glow of the sun at the horizon now for two reasons: I'm a morning person, and love to see the sun come up... and in the NV summers, I can get my outdoor workout in before it gets HOT!  Add one more to that... we've got a great 35 mile bike trail that never shares asphalt with cars.

But, the days of riding in the really dark, dark are gone for me.  I agree with the safety aspect.  Even with the bright clothing and all, I was still hit broadside by a car in broad daylight... any way to make the ride safer is a plus.