I've lived in Los Angeles/the US for 4 years now.

They just started implementing them on some freeways, like I-10 (maybe 2 years ago?). They eliminated the (free) carpool lane and put this in place.

I know city workers who brag about getting their transponders subsidised and get to ride in the cool fast lane.

EDIT: The FasTrak lanes/"ExpressLanes" are actually combined with the free carpool lanes. Sorry for the confusion.

EDIT 2: This is how it works: https://www.metroexpresslanes.net/en/about/howit.shtml

The transponder and opening an accuont (both required) still costs money.

Further info: http://media.metro.net/projects_studies/expresslanes/images/...

I have lived here for about same number of years. I just happened to finally sign up and try it. It was an interesting value proposition. Pay 5+ dollars but remove the stress of possibly being late. The $5 is high enough to make this not worth it as every day default but I am glad to have it as an option in a pinch. Seems to be working well.

They're pretty big, like the size of two credit cards side by side and 1/2" thick. It does make a beeping noise when it registers so that's probably why it's not just a card.

The new switchable pass they're making for the 405 HOT lanes is bigger and thicker. Still smaller than the one in that article, but no longer just a sticker. http://wsdotblog.blogspot.com/2015/04/everything-you-ever-wa...