Dallas is going through a lot of construction right now- and I feel that it's important to let visitors know some important tips to getting around.
635/LBJ Freeway has been under construction for about 10 years. It's an ongoing joke. While it is a major route to get from east to west Dallas, there are a number of ways to avoid traffic by simply taking parallel streets and getting on at the last possible entrance.
The Dart rail is slowly expanding farther north- but it's still really only relevant for folks getting around downtown.
It's fairly unfortunate that public transportation is so lacking here, and that a car is totally necessary in order to get to most places and attractions at a leisurely pace.