Instructions
Think about what material you want to use for the jacket. To maximize safety, you will need to use abrasion and heat-resistant material to protect you in a crash.
Consider the color you want for your jacket. Although black tends to be the conventional, leather can come in the other colors and other textiles are available in any color you please.
Think about how visible you will be when riding at night. Add patches, piping and stitching with a retro-reflective material to your design to ensure you light up in the dark. These can be subtle to avoid ruining the image of your jacket.
Choose between a traditional collar or a racing style collar for your jacket. If you choose to use a traditional collar, decide how you will secure the flaps -- either by adding snaps or thread. The racing style collar fits closer to your body, preventing the entry of cold air. Jackets made with these collars require a soft material around the neck to avoid chafing. Either collar should be tight fitting, but not to the extent that you will find it difficult to move your head to look behind you.
Decide whether you want flexible or rigid armor. Flexible armor is less protective, but allows you more movement. Add armor to your design, on the elbows and shoulders, as well as the spine, if you wish.
Waterproof your jacket by designing the length to beyond your waist. This will eliminate the gap between your jacket and rain pants. Add either a clinching mechanism or elastic around the waist, to prevent the rain blowing up toward your chest.
Design the length of the sleeves, to be long enough to cover your arms, when in riding position. Add elastic, Velcro or zippers around the wrists to keep you warm from the wind.
Keep the front of the jacket short enough that it doesn't protrude in front of you when you are riding. Ensure you design the back to cover you down to the seat of the motorcycle.
Consider how warm your jacket will be, depending on the material you have chosen. If you will need to wear extra layers of clothing underneath, design the sizing of the jacket appropriately for this.