The Intertidal Seaway is a highway in Bikini Bottom mentioned in the episode "Bumper to Bumper." It was mentioned in the middle of the episode when SpongeBob and Mrs. Puff were driving on the road. This highway has 10 lanes, as mentioned in the episode as well.
It was accessed when SpongeBob drove through a "road closed" sign, made a sharp right turn, drove over a field of rocks, and landed on the highway.
The highway then goes into a one lane tunnel through a mountain. Also, in the episode, traffic in this highway is seen to be very heavy.
The Intertidal Seaway is a parody of an Interstate Highway.