Weather. Biking is possible all year round! Beautiful days during the winter, and rainy days during the summer. The weather keeps changing all the time no matter what season. A short check will help planning the day better.
Clothing. Take an extra sweater or jacket/coat. It might get cold and wet later on so better be on a safe side.
Fix kit. It’s recommended to take a reasonable sized pumper and a replacement tube. A compact flat tire kit is available in many shops.
First aid kit. A must. There are many compact first aid kits made designated for camping or road travelers.
Passport/ID. Carry your passport or ID with you in any case the police will ask for it. getting caught without it might result in a fine.
Map. Where ever you’re biking, take a map (if you don’t have a smart phone). You can use the ones available on Gobyx or use your own.
Lights. Front and back lights are mendatory, and because you want to be seen and also not get a fine.
Water and Snacks. Take enough water and snacks for the road. Even if there might be some restaurants on the way, it’s better to have some of your own.
Phone. Just any phone with known contacts and local emergency numbers. In the Netherland's the emergency number is 112.
Sunglasses. And not because of the few sunny days; During summer time and unusual warm days in the winter, bug 'clouds' are flying straight into your eyes/mouth..