Post implementation reviews (PIRs) are an important step to seeing whether projects achieve what they were intended to and to learn what can be improved for future projects. Every year the NZTA conduct PIRs on a sample of projects and for a few years now the NZTA have been publishing the results online. I’ve covered them before here and last year Peter has looked at the trends in them here. Now the results of from 2012/13 and 2013/14 are online and they make for interesting reading. Below are some of the interesting points I’ve picked up from a few of the ones I’ve read.
This project duplicated the existing Manukau Harbour Bridge allowing for 8 lanes of traffic plus bus shoulders as well as widening approach roads and a few other changes. The PIR says the business case for the project forecast that 97% of the benefits would come from travel time savings, 1.6% from reduced crashes, 1.3% from vehicle operating cost savings and 0.1% from reduced emissions (quite how you can get emissions reductions when traffic volumes increase is beyond me).
The report says travel times between the airport to Hillsborough Rd were forecast to reduce by 43% however based on their estimates actual travel time savings are more like 37%. They then that’s a good result as traffic volumes increased by 14%. Unfortunately that in itself is way less than expected as shown by the graph below which looks remarkably similar to some other predictions we’ve seen.
Traffic growth predictions ended up ~45% above the actual volumes of 102k vehicles. I can only assume that had traffic predictions been met that that the travel time savings predicted might have evaporated away. While a few reasons are given for the traffic predictions being wrong, the main blame is aimed at the traffic models and the assumptions within them.
There are some positives though, safety has improved with the annual crash rate falling by 28% which is above the regional average of 24% – although they note this isn’t statistically significant. The biggest positive is the cost which at $218 million was 19% less than estimated ($268m) which is in part due to the project being completed seven months early.
Closely related to the Manukau Harbour Crossing and built partially at the same time, the Mt Roskill Extension saw SH20 extended from Hillsborough Rd by 4.5km though to Maioro St. Again the vast majority of expected benefits (99.34%) came from travel time savings.
The report notes that compared to the 2011 traffic predictions, the actual volumes were 9% lower – although that has grown in 2011-13. Importantly these motorway projects are often partially justified as taking traffic off local roads. The report notes that of the limited monitoring available, traffic volumes on local roads in the area were 21% higher than forecast meaning just a 6% reduction in volumes when it should have been a 22% decrease. So less traffic on the motorway and more stayed on local roads than expected – that’s not a great outcome. Amazingly they also note that no detailed project specific traffic model was produced, instead relying only on high level strategic modelling. This isn’t the kind of behaviour you’d expect for a project costing hundreds of millions of dollars.
There is also quite an interesting comment around the provision of PT. They note that the original documents including the paper that went to the board for funding approval noted that 3m shoulders would be added that could be used as bus lanes if needed. However as built the shoulders are “currently of variable width or absent at some points”.
Another area where the project didn’t perform well was with construction. The project ended up costing $227 million which was 22% higher than the $186m forecast which is blamed on ground conditions, associated earthworks and other items not fully specified or considered in the original tender and consent process. In addition the project was completed one year later than initially expected.
This one is a local road project and involved widening Lake Rd on the North Shore between Esmonde Rd and Hauraki Corner which was said to be to relieve congestion. The reviewers say that in their view, the main issue with Lake Rd is that traffic queues on Esmonde Rd to get on to the motorway but that fact wasn’t recognised in the brief. I guess the planners and engineers involved had their horse blinkers on when working on the project, only focusing on the direct aspect they were looking at.
Economic benefits for the project primarily came from travel time savings (63%), reduced driver frustration (23%) – not sure how this is measured or impacts the economy. Like the other project traffic volumes haven’t been realised and the data available suggests it has actually declined.
The project was originally conceived as a single project but ended up being split in two stages. The total cost was initially $11.8 million however the figure was revised to $16.5 in a new assessment after the small first stage was completed. It ended up coming in 2% less than the revised figure but that was still 37% higher than initially expected
The NZTA fast tracked the widening 400m of SH2 through the Bethlehem Township after the Tauranga City Council received approval to build a roundabout at the western end. They predicted that would “substantially exacerbate existing congestion problems at Bethlehem unless the highway was widened”. Travel time savings made up 88% of the BCR for widening the road.
Despite the widening travel times have actually increased and embarrassingly have done so at the same time that traffic volumes have decreased – as shown in the charts below.
Perhaps things would have been much worse without the widening but it certainly doesn’t seem to have lived up to expectations.
Not all projects have had bad outcomes though. One of the good ones is the Mangatawhiri Deviation which replaced a notoriously dangerous section of SH2. Despite the project cutting 3km off the existing route, 61% of the benefits came from improved safety with travel time savings making up 21%. The impact of the project on crashes is clearly shown below. They also not there have been three minor crashes on the old road which is now a local road.
The shorter and straighter length of road has reduced travel times (although they say there is no reliable base line info to compare with) however they also point out that the exception to this is over holiday periods when there are huge increases in traffic volumes.
The project also came in more than 6 months early and $2.9 million (6%) under the original funding allocation. I’ve long viewed the Mangatawhiri deviation as an example of a project we should be using in other places such as instead Puhoi to Wellsford. It’s also a shame that the current focus on building the RoNS has delayed similar projects east and west of this one.
All up these and some of the ones I haven’t covered highlight some significant issues with our planning and assessment processes. That doesn’t create a huge amount of confidence in me that the same issues won’t be repeated with projects such as the East-West Link or an Additional Waitemata Harbour Crossing – projects that have costs orders of magnitude larger than the ones above. In the case of the latter I certainly don’t think the NZTA should even be contemplating trying to predict things like traffic volumes until Waterview has opened and they have a good handle of the impacts it has.