Easy solution for everyone who doesn't have a sled.
Go to a tire shop and ask if you can take two of their old tires from the trash (free- they don't care).
go to home depot or similar do-it-yourself store- buy three carabiners and several feet of chain, cable, or really cheap, rope, as well as a long bolt and nut, and an eyebolt and nut with washers. buy a short section of pvc pipe.(8-20 bucks approx)
Drill a hole into the tread of one tire, and insert eyebolt, drill another hole into the wall of both tires and insert long bolt holding the two tires together. Using carabineer attach chain, etc to eyebolt and have two equal lengths extending out. Cut pvc pipe into two "handles" approx 4-6 inches wide, run chain through and caribineer them together.
You now have a sled for less than 30 dollars, it's fairly light, but dragging on asphalt in the street is quieter than a metal sled, and has quite a bit of friction. If you need it heavier, slide a piece of plywood between the two tires and fill with rocks or weights whatever.
I made this to keep at home for my upperbody sled days, and on leg days I hook it to my weightbelt and walk around the block.