When a backpack will not cut it and you do not want to fill your pockets with your belongings and risk seeing them spill out, your best bet is to invest in bicycle rack bags. You will usually need to have a rack on your cycle to make sure that common bike rack bags are easy to fit instantly, but this should be something you are interested in adding to your cycle if it is not already a feature. Bike bags can have various shapes, volumes and storage properties. You can buy a basket to mount at the rear of your bike, echoing the kitsch style of having a basket at the front. This provides for easy access to your belongings, although it will give you little protection against the elements.
For a more comprehensive bike rack bag you can choose from a wide selection of options, some of which can be detached and carried easily after you have locked up your bike, which makes them good for commuting or travelling long distances. Internal padding, multiple pockets and storage cubbies as well as durable material on the exterior should be what you are looking for if you want a good all-rounder in this category.
Although many bicycle bags will resist a few splashes of water when you are out and about, you may want to invest in a waterproof cover to keep out the rain, particularly if you are going to be cycling every day. This will complete your bike rack bag experience.