One day, while driving through the countyside, I saw a railroad truck driving on the railroad. As I drove by watching him, I daydreamed about having my own little railroad to drive my truck on, to whatever destination, just by turning on the cruise control and letting it go on its own.
you are familiar with the toy track cars, that follow a track and fly around the track's turns. I began to mix the two concepts together.
If trucks can drive on railroad tracks, and toy cars can use a rail to race around a track seemingly impervious to g-forces and traction, then surely vehicles on an interstate can as well.
The right lane is where most traffic stays, apart from passing. Using the same exact railing from train tracks, a rail can be embedded down perhaps a foot into the road itself. Drains at intervals keep the track from flooding. Periodic cleaning by a vacuum equipped street sweeper keeps stray gravel from collecting.
To mate the cars to the track will be quite simple. An assembly resembling an arrestor hook on naval aircraft is suspended from the bumper/frame of the car, in front of the front tires. This allows steering to be a non-issue, the tracks will guide the tires straight, or whichever way the track happens to be going, due to the caster effect of steering design.
The assembly itself has a rubber wheel, encased by steel, to resemble a train's wheel but with rubber as the contact patch and steel sides surrounding the track to keep the wheel locked on. The assembly is lowered through manual means, via a cable to pull the wheel down. Springs are tensioned so if the cable breaks, you're not stuck to the rail, it retracts itself and you resume normal driving.
Another fail-safe is the adverse angle disconnect. The assembly rests on a lobe shape similar to a cam. If your car happens to get sideways, the assembly will keep tracking with the road until it slides off the lobe, allowing the assembly to retract on spring force and disconnecting itself from the track.
Getting on the track requires no superhuman driving abilities either. Rather than extending the assembly onto the road and cutting it up with your steel wheel, another small wheel keeps it from contacting the ground. Once extended, it rides on this little wheel until it gets into the track groove. The large wheel makes contact and hooks up, while the small wheel no longer has any ground to touch due to the 6" height of the rail. Just a simple extension, wander around the center of the road until the wheel falls in.
Passing is simple as well. Just release the lever, disconnect, pass the car, and reconnect again. It's almost as simple as putting on your blinker.
Although the track canal is small(a typical train track is 3" wide, and the wheel together make it 4", add another inch on both sides for leeway to make it 6"), and cars would pass over it with ease, motorcycles on the other hand would need their own lane. Something on the order of a few extra feet width to the interstate to make the shoulder another smaller lane(similar to bike lanes), while retaining ample room for emergency use of the shoulder.
This road design can be improved upon through use of anything from contacts relaying mile markers, road identification, mileage to different cities, to track sensors that relay speed to police officers.