Okay, so you've got a dog running around without a leash and one that won't let you catch him?
I'd suggest taking what some of the other users have said very seriously, but one more thing that you may want to do is something that I train all my dogs to do: love car rides.
Every dog I've ever owned in my life has been trained to get into a car without a leash. You can do this with treats if necessary, but most of the time it is not. If they ever get out and start running around, you can just open up your car door and they will come. If they don't believe you, just get in the car. They'll know you're serious.
One thing I wanted to add. You may not even need to train your dog. Try it in your backyard or in a park somewhere. Just park your car on the green and get out and play with him for a few minutes, being sure to get him all riled up and excited to play hide and go seek. Then stop abruptly and start walking towards your car with the leash, and yell "Come on! Car time" or something to that affect -- be sure, whatever you decide, that your command:
- Has two syllables (i.e. "Come On, Car Time!") . Animals respond better to words with two syllables, for some reason. I don't have any empirical evidence to support this, but through simple observation you can clearly see it.
- When you're yelling a particular command, yell the same exact command, over and over again and in a rising tone and higher pitched voice; because, rising tones correspond to happy expressions and a high voice corresponds to excitement.
- If you have a command that you use, like "Cage" or "Kennel," (which means "get in __") you can try using that command, if the dog responds well to it. You can attach the word "Car" to "Cage" but not to "kennel" because that would violate the two syllable rule.
Every dog that I've ever owned has been trained not only to "kennel" and "car" but also to walk without a leash. It is inevitable that a dog will escape sometimes. The reasoning is that Alsatians can be particularly dangerous, especially when the chase instinct kicks in, and I don't want them maiming some innocent child. The force they can bite with can shatter a cow femur -- I've seen them do it.
On a less serious note, car rides to fun places are a really good motivator in getting them to go into a car. Just like anything else, you have to use operant conditioning to ensure the dog will behave as desired. You can do it, even if it is counter intuitive, such as a feeding thing.
I once trained a dog to not eat their food until I say so. Call me cruel, but I once set the food bowl on the ground and folded laundry for half an hour. I came back to a puddle of drool on the floor and the food not missing. They knew that if they waited I'd give an extra slice of bacon or a treat in addition to their can.
It's all operant conditioning: obedience brings positive reactions, disobedience brings negative reactions ten times as severe as the reward for positive actions. Good luck, you can do it!