What's an Echelon?

An echelon is a form of drafting between riders when there are cross winds (slightly slanted head winds) active on the course. Riders will form a diagonal line facing the cross wind such that they gain the maximal benefit of draft.

You can basically think of it as how the peloton drafting advantage works but on an angle.

When do cross winds generally occur?

Early in the season during the Middle East races like Tour of Oman or UAE Tour, cross winds and hence echelons are quite common. Early spring races in March or April in Belgium often generally have cross winds.

Lighter riders may be drastically affected by these cross winds if they fall out of the peloton. So much so they can basically be blown over. It's worth taking note of the cross winds when placing bets.

Teams will be less likely to take risks and form breakaway groups if the cross winds are high. They also won't want to "work" on the front all day and it may end up causing the entire races to drastically slow down if no one wants to work until closer to the end of the stage.