Is there a way to know if someone is drafting behind without turning your head back or trying to hear the noises?
A group riding together and cooperating will ride to a set speed, so you'll be surging if you exceed that speed for long.   A simple wheel-magnet speedo and bike computer helps show this on your bars without being big or expensive.

An ad-hoc group will ride with varying speeds depending on who's in the front and whether they are trying to make a break away or if they're just sick of waiting for the rest of the group to cycle through the paceline. 

Some riders need short pulls and some can cope with long pulls at the front.  Separately some people need short rests out of the wind, and some people require quite long periods behind someone else to regain their pace.   

The best groups work together for the end goal which is a good training ride.

In racing, your team is your group and the other teams are NOT your friends so they're working for themselves.  A race peloton is therefore an adhoc group of teams who are not working together.



If you face some decent climbs in your route, then groups tend to fall apart as everyone climbs at their own pace.  For training and bunch rides, stop at the top and let everyone get there, then rest till the last arrival is ready to carry on.

Otherwise the first arrivals are rested while the last people are shattered and the group breaks up or is held back.

Same goes for downhill - strava segments work on segment time, not first-down time :)



More thoughts - A shoulder check every half minute should show you if the rest of the paceline is there still.

If you don't have a speedo, riding to a set cadence might be enough.  Try and memorise the speed of your feet while in the paceline, and simply maintain that rhythm when you hit the front of the line.  Sing a song in your head of the right speed, or count off like marching if that works for you.

Getting expensive - there are race-radios like the pros wear.  They are essentially Personal Shortrange UHF radios with an earpiece and a small transceiver in a pocket.  The aerial/headphone cable runs up the back and is often taped on.  Some new ones are small enough to work with the helmet.  These talk to each other in the team and to team car, who then relays messages onwards with a second radio or maybe a cellular phone.   Some are even bluetooth based and just associate with one~four other units.   Motorcycle riders might wear these under their full face helmets.