Hard working 2 lanes roads

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In Hamilton, a 10m-wide 2-lane road can move over 30,000 vehicles per day (vpd). A 6m-wide 2-lane road between obstacles (wall or parking) moves just under 20,000 vpd, and a 5.7m-wide 2-lane road moves just under 19,000 vpd. Fairfield Bridge is an example of a road at maximum capacity. For 14 years out of the past 20 the number of vpd has been between 19,000 and 20,000, but never above 20,000 vpd. Short-term reduced access to bridges north or south and changes to intersections at each end had little effect on vpd counts on Fairfield Bridge. Placing the above fact alongside ‘Lane Capacity, Table 6.2’ below, which shows Fairfield bridge, with its 3.0m-wide lanes and no obstacle-free shoulders, has a capacity of 58% of an ideal 3.5m traffic lane with a 1.8m obstacle-free shoulder,

The above calculations can be repeated on the Kahikatea Drive rail crossing count of 31,200 vpd, which is 92% of the ideal 34,000 vpd on a road width of 10.6m. However, unlike the Fairfield Bridge, the vpd numbers on Kahikatea Drive and Cobham Drive continue to increase, showing it is possible for a 2-lane road to move over 30,000 vpd.

Traffic counts can be found on Hamilton City Council web site, under Our Services/Transport/Maintaining and Replacing/Traffic Counts

Victoria/Anzac Bridge is another example of a road at maximum capacity. From the mid-1990s, the vpd count was in the vicinity of 28,000. It peaked at 29,050 vpd in 2005, then declined to the mid twenty thousands over the past 15 years. Placing this fact alongside ‘Lane Capacity Table 6.2’ the Victoria/Anzac Bridge with its 3.3m-wide lanes, with 1.2m obstacle-free shoulders has a capacity of 85% of the ideal 3.5m traffic lane with 1.8m obstacle-free shoulders. The peak value of 29,050 vpd is 85 percent of 34,000 vpd.

Victoria/Anzac Bridge prior deck widening

In the 1970s, the Victoria/Anzac Bridge lanes were 5.7m wide and moved 18,900 vpd. Table 6.2 states this is half (‘49%’, see foot note) of what an ideal road would move (18,900 vpd is 49 percent of 39,000 vpd).

You can access the new Traffic Count Viewer HereOnce the WebMap is opened you can click on any of the orange dots to open up all the data that is available for that particular site.

My Traffic Flow table includes a column titled ‘Theoretical Percentage Efficient’, which is to show how hard the road is working, whether it is under-used, and whether it could be narrowed without reduced vpd capacity. I will refer back to this in a future post.

Foot Note: The Power Broker – Robert Moses :by R A Caro‘He was very careful always to have his facts ready, never to exaggerate them and always draw from them logical conclusions (p4) … When Mr Moses says something will cost 3.4 percent, he adds the .4 only to make you think it’s accurate (p502)’. Using 49% instead of 50% on Table 6.2 make you think it’s accurate.

Past post on traffic lanes:







Category: News

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