M5 East Broadcasts
Was driving back to Camden tonight through the M5 tunnel. Traffic was backed up due to late night roadwork. The radio was playing along nicely when all of a sudden a voice cut in through the transmission. “This is the M5 East traffic control room…” a voice intoned. An apology for the roadworks followed, and then the music cut back in. The transmission repeated every minute or so. Flicking between radio frequencies and AM/FM bands gave a “do not adjust the dial, we control all the frequencies” type effect. It’s the first time I’ve heard of it, but it sounds like they have some sort of radio jamming device they can use to broadcast over normal channels while you’re in the 4km tunnel. While I appreciate the intentions, can you imagine how annoying it would be to be listening to the news, then the cricket scores are about to be announced when suddenly… “This is the M5 East traffic control room.” It sort of defeats the purpose if their apology ends up pissing people off instead.
1:18am (GMT +11.00) tomorrow 
It’s not a jamming device, most of the bigger in Sydney tunnels have a AM/FM Rebroadcaster. You’ll find that some channels like the community stations don’t get repeated at all in tunnels, while most of the major ones are. All they’re doing is cutting over their repeated transmission in the tunnel.. in fact, it’s their right too as they own the transmitters in the tunnel anyway. Not sure if the commercial stations pay to have their signals repeated into the tunnels or not..
http://www.google.com/search?hl=en&lr=&ie=UTF-8&oe=UTF-8&q=am+fm+rebroadcast+systems+sydney+australia&btnG=Google+Search
Yeah tell me about it. Even during normal traffic they have a “this is a test” kind of message playing periodically – I must use the M5 a lot more than you. :)
It’s thoroughly satisfying when you come out of the tunnel half way through a message, and it cracks up and is replaced by music – it’s like you’ve conquered the Voice.
Happens in the Harbour tunnel as well. I’ve been in the HT when a Computer Voice told me off an accident ahead. Generally when they tell you, its too late, but at least you know why you ain’t moving.
In hindsight, yeah, FM signals do not penetrate structures such as car parks easily, and AM signals fare only marginally better, so a rebroadcaster is logical. Broadcasting over a signal would still leave the old transmission playing in the background? And jamming just involves broadcasting white noise over a frequency?
At least you Aussies get the fairly useful signals. Now some US company has decided their billboards need to jam (yes jam) signals and broadcast ads when people drive by them. I simply can’t wait till friday, then I get to hear the stupid things.
I-5, here in the US, travels the west coast. I, for one, would love to have traffic things locally sent over the FM or AM airwaves. As it is, there is a channel for traffic information, but it plays the info for the whole region (something like 300km radius). Not useful at all.
i was once in the m5 for one and half hours on my way to unsw. someone 3 cars in front of me had an horrific accident, and while they did whatever it is they do (it involved emergy crews), they played a recorded message every minute. We were instructed not to turn off our radios, but switch off our engines … the end result? The monotonous sound and the overload of carbon monoxcide made most of the people sleepy and the remainder of the trip extremely dangerous. In the future I’ll put on a tape when there’s an accident, the voice says nothing of great importance anyway.