The pictures below are of my SensorHarness I make for wood and plastic tracks. The SensorHarness can be any number of lanes and with the fairly simple installation you can be up and running in no time.  The requirements on the PC side are minimal, any Pentium 100 with Dos and a working parallel port can be used.

Below is a picture of the sensor.

Here is the top of the PC Board.

Here is the component side of the PC Board.

Mounts.

The complete package, 4 lane SensorHarness, AC Adaptor and Computer cable.

Here is a picture of the mount needed in your MDF track.

The SensorHarness can be used in wood or plastic tracks however it is designed for wood tracks. The benefit for plastic track users is for the track owners with hard to find or discontinued track. With the SensorHarness you can install the sensors in an evening and not have to send your track out for the installation. The Installation on wood requires a slot be routed horizontal to the track slot and the sensors dropped into place and some hot glue added to hold them in place. The installation on plastic is some what more difficult and a dremel would be a necessity.