The other day I wrote about the need to fix the Symonds St on-ramp. In the post I included a graph looking at average daily traffic volumes on it over the last 15 years. While pulling the data together for the graph I thought it would be useful to compare it to other city centre ramps. It also struck me that while I’ve looked at motorway volumes in the past, I’d never really looked at motorway ramp volumes before. In taking a look at them I found some fascinating results.
First, here are the ramps I included in this analysis. It includes all ramps that enter or exit near the city centre. I’ve included Khyber Pass and Newton Rd in this due to their proximity to the city.
- Fanshawe St – On and Off ramps
- Cook St – Off-Ramp
- Wellington St – On-Ramp
- Nelson St – Off-Ramps, separately for both SH1 and SH16
- Hobson St – On-Ramps, separately for both SH1 and SH16
- Symonds St – On and Off ramps
- Wellesley St – On and Off ramps, separately for both SH1 and SH16
- Stanley St – for traffic between Alten Rd and Grafton Rd, excluding those using the ramps to Grafton Rd
- Khyber Pass – On and Off ramps
- Newton Rd – On and Off ramps
First up, let’s look at the totals of all of the on and off ramps combined. What you can see is, particularly over the last decade, surprisingly little change. Volumes in 2016 are slightly lower than they were in 2001. That’s notable because the city has changed tremendously over the last 10-15 years. Since 2001 the number of jobs in the city centre has increased by close to 40% (almost 30,000) to around 110,000, more in the wider area served by some of those ramps. Education has almost certainly become a larger contributor to the city and of course there are many more people coming to the city for retail and entertainment. Of course, there are also many more people living in the city.
One aspect I’m not clear on is why the on-ramps have consistently more traffic than the off-ramps. Is it that people are driving to the city on local roads then driving home via the motorways?
Notably the view that traffic remains largely the same, or slightly down is also seen in other statistics, such as AM peak trips to the city. The one transport thing we do know has changed considerably over that time is the number of people using public transport (walking and cycling are also increasing).
While the overall volumes have been relatively flat, there has been considerable change at an individual ramp level. One of the most noticeable of these is the significant changes to the Wellington St and Hobson St (to SH16) on-ramps and also to the Cook St and Nelson St off-ramps. This occurred in 2007 when the direct motorway to motorway connections were made, saving drivers from having to pass through the southwest of the city centre which is also responsible for the overall dip in the graph above. To highlight this, the graph below looks at the volumes for just the Wellington St and Hobson St to SH16 on-ramps. The same pattern exists for the corresponding off-ramps.
Overall it represents 10-15 thousand fewer trips passing through the southwest of the city centre. That’s an area currently undergoing significant redevelopment to apartments and so we need to be looking at how we can take advantage of that freed up road capacity
Another trend I noticed was the decline in traffic on the Fanshawe St ramps. Some of this will have been due to the motorway works mentioned above providing access from the North Shore to Grafton Gully, spreading some of that traffic out. However, those links have been in place for over a decade and you can see, volumes have continued to decline over time.
One aspect that has changed on Fanshawe St over this time frame has been the introduction and continued growth of the Northern Busway and other bus services from the shore. I wonder how much of a role that’s played in in these changes.
The graph below shows the results for all of the motorway on-ramps. As well as the changes mentioned above, the other two most significant changes have been in Grafton Gully with both Stanley St and Wellesley St growing over time since those connections were built in the early 2000s.
The overall trend looks very similar to the on-ramps graph. A couple of other changes include the growth of traffic on Nelson St from SH1 but that seems to have offset traffic from SH16 – although I wonder if the 2016 number is the result of a data error given its sharp drop.
What do you make of the numbers?