http://www.signonsandiego.com/news/northcounty/20041229-9999-1n29wild.html (http://www.signonsandiego.com/news/northcounty/20041229-9999-1n29wild.html)

QuikQuote: By spring, park officials expect to begin construction of the wheeled tour system. The existing electric monorail route will be split in two, with one half continuing the rail operation in a smaller loop while crews revamp the other half for wheeled vehicles. "Intelligent" vehicles – fueled by hydrogen, electricity or a hybrid system – will follow a route guided by wires embedded in a raised roadbed. The tour guide would not need to steer, but would be able to disengage the vehicle and leave the roadway in case of an emergency. Both tours will be about 25 minutes long, less than half the time visitors now spend on the monorail. Surveys showed that patrons preferred shorter tours and wanted to get closer to the animals – one of the goals for the new system.

that's a shame... that truly was a unique experience. I grew up near there, and the tram was a life-shaping thing for me and my frequent companions in crime, my nieces and nephew. (my oldest niece is just about to graduate with a degree in enviromental science)