I use "ClearTheWayV" (which also helps traffic avoid you while out of your car making a traffic stop), and the barriers that come with Police Radio. "LCtrl+J" to place, "J" to remove. It's a little immersion breaking to have to place a barrier, but I rather that than being run over. Another useful mod is "Traffic Control", which lets you slow traffic to 10MPH or stop it completely.
Links to all three: