I decided to just change this thread to a Roads Fantasy Thread now that everyone is throwing concepts all over. Besides, the HWY 99 timeline and speculation is at the current stages, a concept.
Quote:
Originally Posted by allan_kuan
Are you talking about my curving tunnel or the one that jsbertram made?
For mine, the ramp entrances could be adjusted somewhat to make the traffic flow smoother. Of course, I'm no traffic scientist or geologist, so this alignment will probably change by the time someone comes by to build it, whenever that occurs. =S
The curving of the tunnels to follow the surface is mainly to address the fact that tunnels with any kind of cars in them need ventilation shafts. Locating them near roads makes building them (and some emergency exits along with it) much easier.
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Yes, I was referring to yours. But before I respond, I admit I do have a personal bias against roadway expansion unless I see it is absolutely critical. If you ask me, while I agree that there should be a tunnel to replace the Lions Gate, I do not see the need for a tunnel through the core.
Anyways, back to my point earlier, the choke points will occur because of the number of exits throughout the core. Looking at your map, we have an exit at Alberni and Pender Street Southbound. Alberni, remember, is more of a local street: it is not designed to handle as an arterial. And because Alberni is used as a exit point, drivers will use Alberni to get to other local roads roads such as Burrard and Robson Street, and thus, increases traffic on these local streets. Yes, it may reduce traffic on Georgia, but it doesn't reduce net traffic, it simply redistributes it onto local collectors.
Continuing southbound through the curve area, there is a total of three access points into the tunnel, all within a very short distance of one another. Unless you are proposing for exit to have its dedicated lane into the tunnel, this doesn't allow for longer acceleration lanes and requires drivers to make merges immediately into the main tunnel, which will cause traffic bottlenecks. The perfect example of one in the Lower Mainland is Knight Street and the Bridgeport Cloverleaf. The one reason why traffic slows down to almost a stop is not really because of the number of cars using Knight, but the fact that short acceleration lane forces an abrupt merge.
Next potential problem is the exits onto Fir and Sixth. Again, these aren't roads that are designed to handle more traffic than it already is. For Fir, the significant elevation change between Sixth and Broadway poses a construction challenge, not to mention, the Fir Street overpass.
Going northbound now, again 12th and Broadway entry points are within a short distance of one another, which poses short acceleration lanes and tight merges. These turns are also quite tight. On a normal cloverleaf, it might be acceptable because you have a larger field of vision, but in a tunnel situation, it can be much more dangerous.
Nelson and Hornby is also within a short distance of one another. If Nelson is taken away, for instance, how much harder is it to drive two blocks on Hornby to access Nelson?
Then, we also have Melville and West Pender entry points within a short distance of one another.
I didn't mention space required for these tunnel portals. It's one thing to draw a bunch of lines on a map, it's another to factor other information in, like topography, property acquisition needed, etc. For instance, Georgia Street isn't that wide to have room for a tunnel portals: it will come on the expense of other traffic lanes of pedestrians.
If one is proposing any tunnel through the downtown core for commuters to/from the North Shore, it should bypass downtown, with maybe a maximum of two entry and exit points in the core. Keep in mind, your proposal also reduces traffic on Granville Bridge, one that is overbuilt at its current state. I'm not sure what you meant by rebuilding the bridge, if that is even necessary.
Really, if people are going to downtown, they should only have a choice of using the bridges and not the tunnel. If people want to bypass downtown to the northshore, they should only use the tunnel.
Keep in mind though, I still don't support a tunnel going through downtown as I do not see the need for one.