Do not attempt to transport them in water. Get a tupperware plastic container, punch holes in it, and line the bottom with damp paper towels. If the newts have live plants, place the plants in the container. Put the container in a cooler with some blue ice cold packs, and keep cool throughout the trip. Never leave the cooler in a parked car.
To avoid an abrupt change of water, take along a gallon jug of their previous tank water. When you arrive, set them up with this gallon of water. Then add fresh dechlorinated water gradually.
Do not attempt to transport water (or newts) in the tank itself. The sloshing is incredible.