The Bicycle Defense Kit (BDK) offers options for dealing with aggressive motorists. Contained within an altoids tin, the 8 tools vary in detectability, potential to cause damage, and legality.

Specifically, cyclists can:
1. Issue "citizen citations" with official-ish tickets.
2. Label offending vehicles with an "I was a jerk to a cyclist" sticker.
3. Introduce the risk of paint damage with a Jolly Rancher.
4. Create certain coating cremation via DOT3 brake fluid.
5. Make cars stink worse than their exhaust with a carefully-placed stink bomb.
6. Throw a trusty bolt to dent offending traffic as it passes.
7. Lock out loony drivers by filling their keyholes with super glue.
8. Cut through tire valve stems with a utility blade.

It goes without saying that you shouldn't do anything you're not fully prepared to take responsibility for. This project is meant to increase cyclist confidence, not fatalities.

You can order one made by me for $20, or build a cooler version yourself for ~$10.

Step 1: Set Your Design Goals

This is a universal that I'm slowly and surely trying to integrate into projects. Sometimes, I even remember to think about what I'm trying to build before wasting a lot of time making the wrong thing:)

My main goals with the BDK were:
1. Cost: <$10 in parts and very little time to build so I can happily sell tem at $20 each.
2. Size/weight: small/light enough that people might actually carry it.
3. Subtlety: objects close enough to everyday detritus as to permit "plausible deniability."
4. Variety: different severities of revenge will help me ride more confidently and encourage fair responses by cyclists. U-locks should sometimes meet windows, but these occasions ought to be few and far between.

Next, I kinda just brainstormed and experimented until I was happy with how close I got to ghese goals. Here's a much better overview of the design process than I can provide.

Step 2: Get Your Ingredients

Here's what was used to create the BDK:
Paper for parking tickets: I used a thicker orange stock, to make it look all nice and official-ish
Sticker material: these were laser-printer-compatible rectangular stickers, ~3"x5"
Contact lens case, preferably with thin plastic so you can cut it in half
Brake fluid, DOT3

Stink bomb materials:
Valerian root capsules: 100 for like $9 at Walgreen's
Vinegar, white
Salt

Syringe (to make it easy for moving brake fluid and stink bomb juice)
Bolt, slightly shorter than length of altoids tin and nice and heavy.
I think I used 4"x3/8"
Super glue: generic at Walgreen's is way cheap
Jolly rancher. The car won't care what flavor:)
Utility blade. Something like 10 cents each when you get a case of 100 at Home Depot
Altoids tin case. Use one after eating the altoids, or buy a little metal case of your choosing.

Step 3: Prepare Stink Bombs

Nothing too complicated here: valerian root + vinegar + a little salt = stink bomb. Initially, I cut the valerian root capsules open. Then, I realized how much easier it'd be to twist one end of the capsule until it comes off. Mix it together, and you're good to go. Not too stinky initially, but I think it's approximately rotten flesh after a coupla hours exposed to air...

Step 4: Fill Stink Bomb and Brake Fluid Chambers

This is where the syringe comes in handy. Note how many milliliters of material fit in a contact lens case to make it easier for filling multiple containers. Close the lids tightly, rinse in between as well as afterwards, and of course make it clear that the syringe and lens cases shouldn't be used for non-bike-defense purposes...

Step 5: Create Citations

I wanted to make the citations a balance between official and philosophical. For me, this meant coming up with an official(ish) front side and a lengthy philosophical explanation on the back.

Click on the pictures for images of the front, back, and 3-per-page layouts (pdf).

Step 6: Make Stickers

Mine say "I was a JERK to a cyclist", but feel free to come up with your own. I've had suggestions for "I was a jerk to a stripper" from another pedicabber and just a big "D" (for pasting over the "H" in Hummer). Source files below.

jerkst.pdf
Download

Step 7: Pack It All Together

After grabbing the rest of your ingredients, stuff it all into an Altoids tin or whatever container you choose. I like organizing the contents so that one needs to go deeper into the tin, consciously choosing not to use less controversial remedies like a citation, before reaching the serious stuff. Chunks of bike tube can make a convenient attachment device for carrying on your handlebars / belt / wherever. Also, make sure you're not building an uber-heavy kit nobody will ever carry on their bike.

Step 8: Use, Wisely

Screwing up somebody's beloved paint job can be serious stuff. Doesn't matter how fit you are if it's car vs. cycle: the 4 wheels tend to win. Don't be stupid about this. Ride safely, confidently, and, when it's warranted, vengefully:)