You too can contribute to your own good health and carbon reduction on Earth. Dust off your bike and go riding this summer. This Topeak trunk bag for your bike easily slides onto a bike back-rack also sold by Topeak. No hassle no mess. Normally a very compact trunk bag, the sides fold out as shown in the picture into more room for your books, laptop, groceries, etc. Yes, I can fit my regular sized laptop into this, as well as half a week's worth of groceries. The trunk bag comes off the bike's back-rack with one click and has a shoulder carrying strap for carrying around.
I installed the associated back-rack in 15 min with no help and one allen wrench, then spent 5s slipping on the trunk bag, done! Then I went bike riding with my friend, shopped with it at my neighbourhood grocery store and met the nice folks there. And then we got ice cream! What speaks summer more than riding around on your bike and stopping at the ice cream store? While you're at it, bring your laptop and get some work done at the local coffee shop! Give up your car and get out there on your bike this summer!