[jnaas2]

Sorry the picture turned out so big but as you can see from the picture they used a short sweep 90 where the 1 1/2 inch pipe turns out to accept the p trap. The reason for not using short sweep 90s on horizontal pipes is that you will lose the velocty of the water flow as it turns the short sweep, but this is where the water starts and the velocity is usually high since it just dropped vertically from the sink. The tee with the other tee directly above it for the double sink is unusual, but they do make a double sanitary tee with a connection on the top for the vent line to connect into the drain