Quote:
Originally Posted by DigitalNinja
I don't think that the per lane use of measure is very good. Anyone in all of Halifax can use the bridges any time of day. Also I'm not too sure about those other cities that you mentioned but I would think that the way Halifax is laid out people cross from both sides to get to work. There is a lot of business in dartmouth and burnside but also in halifax peninsula. Also the metric for measure on a bridge like the McDonald would be different as well. It's a bridge that doesn't lead to any highways it goes straight to downtown streets that can't handle a high volume of traffic. Where as Vancouver bridges or montreal can mostly lead to highways Halifax bridges really don't besides one side of the Mckay. This aspect alone greatly reduces the amount of traffic each lane can handle.
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I remember reading a publication in Thunder Bay a while back that showed the capacity of each lane in a given class of road facility:
Local road: 200 vehicles per hour/lane
Collector: 400 vehicles per hour/lane
Minor Arterial (HRM Major Collector): 600 vehicles per hour/lane
Major Arterial (HRM Arterial): 800 vehicles per hour/lane
Expressway: 1000 vehicles per hour/lane (widely spaced traffic signals like on Burnside Drive)
Fully Grade-separated Freeway: 1200 to 1800 vehicles per hour (a vehicle every 2 to 3 seconds in each lane)
Even in a fully grade-separated setting, when you have a ramp that is of such low design speed such that the necessary following distance between vehicles exceeds the amount of distance that can be traversed at the design speed of the affected ramp, such as on the tight, 20km/h hairpin ramp from outbound Bedford Highway to southbound Joseph Howe Drive, it takes a lot less traffic to cause back ups than it would on a 40km/h or a 50km/h ramp. I have seen the Joe Howe ramp itself back up a lane of traffic to the point of both backing up the Windsor Street Exchange (which already has its own backups) and tying up the westbound lanes of the MacKay Bridge. Joseph Howe Drive is a very busy access to Fairview/Clayton Park (hence the need for the Lacewood Connector) and also a busy switch-over between Highway 111 and 102 (hence the need for the viaduct freeway link between the 111 and the 102).
The MacDonald Bridge is like a mile long, 50km/h freeway that receives its traffic from and dumps its traffic directly onto roads that are, at most, Arterial class roads that cannot handle more than 600 vehicles per hour in each lane, due to impediments along these affected roads that hold up traffic from dumping off of the bridge such as traffic signals, intersections, driveways, RA-4/5 crosswalks, etc.
Regards,
Richard Kannegiesser