Scenario 1. You meet friends for an early dinner, expecting to arrive home before dark. The food is good, the conversation is better, and before you know it the sun is going down. You have to excuse yourself early and run home before it gets dark because you didn’t put your lights on your bike.
Scenario 2. You’re running up against a deadline at work and you end up staying two hours late to get the project out the door. By the time you leave it’s dark outside. You gear up, take your bike out of your locker, and when you turn on your headlight the battery is dead.
Scenario 3. The train is delayed an hour due to construction on the main line. By the time you reach your stop it’s dark outside. You don’t give it another thought because you have a generator hub and dedicated headlight and tail light. You flip a switch and ride home, fully illuminated and safe.