I also live in Dallas and did the commuting thing last summer and most of the year until recently. Now I just take DART because riding offroad and commuting was causing nerve damage in my hands. Here is what I recommend: Get a used bike of some kind. It's not going to make much difference for 4 miles. I commuted 10 on a MTB with bar ends and skinny tires. Rack and panniers is ideal but a backpack also works. Roll your clothes to keep them wrinkle free and buy some "wrinkle release" spray if you need to look really pressed. Dress cool but you don't need cycle clothes for 4 miles. If you have flex hours, leave early in the morning to stay cool. Use baby wipes and deoderant to clean up before changing. Cool down by taking it easy for the last mile or sitting inside for 15 minutes before changing. If you're hot, you'll keep sweating after changing. You'll have to spend some money but it is way cheaper than driving.