Aren't Bikes Traffic?

On a ride around Lake Washington, I began to notice the signs. They occurred mostly at construction sites, and re-directed bikes where the bike lane was closed. It’s nice that they now put up signs, where in the past they simply roped off the bike lane or parked a big truck in it. What I didn’t like was what the signs said:

“Bikes merge with Traffic”? What do they mean? Aren’t cyclists part of traffic? Can you imagine a sign on the freeway saying “Right lane ends. Trucks merge with traffic”? Of course not, that would be absurd. Do traffic engineers or whoever designs these signs still consider traffic to be cars, and cyclists to be secondary users who don’t really belong on the roads?

And then there was “Road closed to vehicles,” with the clear implication that bicycles are not “vehicles.”
To be sure of the meaning of “traffic”, I looked it up in Webster’s Encyclopedic Unabridged Dictionary of the English Language:
traf•fic: 1. The movement of vehicles, ships, persons, etc. in an area, along a street, through an air lane, over a water route.
The definition said “vehicles,” not cars, so now the question was whether a bicycle is a vehicle or not:
ve•hi•cle: 1. any means in or by which someone travels or something is carried or conveyed.
There is nothing in either definition that indicates that bicycles are not vehicles, or not part of traffic. Yet the signs imply that vehicles are only cars and trucks, and that traffic does not include bicycles. And since roads are intended for traffic, they are not intended for bicycles.
Some might say that this is just semantics, but I am concerned about the attitude this implies – an attitude that remains all too prevalent among drivers. Why not simply say: “Bicycles merge left”?
Or perhaps we should just get rid of the merging instructions altogether. After all, if you see a sign that says “Right lane closed” and you don’t know that you need to merge left, you shouldn’t be driving a car or riding a bike! “Bike Lane Closed Ahead” really tells you all you need to know!

As to the “Road closed to vehicles” sign, a better way could be to keep the “Road Closed” sign and simply write on the other sign “except pedestrians and bicycles.”
I am not so much concerned about the signs themselves, but about the underlying attitude they represent, that bicycles aren’t vehicles or traffic and don’t have equal rights to use the road.
What do you think? Do you have better ideas for a concise message to write on these signs?