Danger on a bicycle
A metal structure below the human body increases the danger of a lightning stroke. A cyclist forms a rising point in flat terrain, which can act as the origin for a connecting leader. As a consequence, the cyclist will be the striking point of the lightning.
Lightning searches for good conducting metal objects and the cyclist will be in the direct current path to the bicycle. The lightning channel produces hot spots at the contact points to the metal structures, and therefore the lightning can cause heavy burns at such places.
When there is no safe place (such as a building) in the vicinity, it is acceptable to ride towards a tree, leave the bicycle and stay at a safe distance from the tree. It is important to know that the first lightning strikes appear before the rain and any intention to take refuge away from the rain in open country occasionally increases the danger of a lightning strike.
Safety can be enhanced by crouching down in a similar manner to walking people. When no protruding object is in the vicinity, the only other possibility is to lie down on the earth. However, it is advisable to leave the bicycle at a safe distance, because its metal body increases the danger.
Tibor Horváth, Understanding Lightning and Lightning Protection