Asphalt or chip seal – the vexed question

Commision News & Views
with Commission Chair
Anne Tolley

One of the most frequent complaints Tauranga City Council commissioners receive is from people expressing dissatisfaction that the asphalt road surface in their quiet suburban street has been, or will be, replaced with chip seal.

On a purely aesthetic level, this is perfectly understandable – asphalt (also known as hotmix) provides a nice-looking, flat black surface which creates minimal road noise. The roads in many Tauranga subdivisions are surfaced in asphalt, purely because it is a good selling point.

Asphalt is also resilient, long-lasting and usually requires little maintenance during its normal lifetime.

The problem from council’s perspective is that when that lifetime is nearing its end, asphalt is expensive to replace and that cost is further increased because the normal 51 per cent subsidy arrangement does not apply if the much-cheaper chip seal option is considered (by Waka Kotahi NZ Transport Agency) to be ‘fit-for-purpose’.

The net result is that a ‘like-for-like’ asphalt replacement on a street that doesn’t have high usage or carry a lot of heavy vehicles (two of the main factors that determine whether or not the work will receive full subsidy funding) can end up costing council several times what a chip seal surface will cost.

That cost difference raises an important equity question. Is it fair for people who don’t have the benefit of having asphalt surfaces on their streets to pay additional costs through their rates to maintain that privilege for others?

We’re not talking about a small cost. If we resealed all of the existing ‘end-of-life’ asphalt roads in the city with new asphalt surfaces, where that surface can’t be justified by road usage factors, it would add around $2.5 million to our road maintenance costs every year.

Council’s resealing policy is therefore that asphalt should only be used on roads where it can be fully-subsidised, due to high traffic volumes, heavy vehicle numbers or in locations where there are high turning stresses on the road.

A quick ‘primer’ on road sealing: roads are sealed to eliminate dust and provide a safer, smoother surface for vehicles to travel on, but a key purpose is also to protect the ‘pavement’ – the very expensive compacted layer underneath the surface – from being damaged by rainwater.

Chip seal does that just as effectively as asphalt, which is why it is considered fit-for-purpose in many situations.

Some of our recent complaints have related to seal quality, either because the chips used have been too large and have resulted in much higher road noise, or because they haven’t been bound effectively in the road surface (or both).

Many of those complaints have been justified and the contractor responsible has been required to fix the problems involved.

Council is currently securing a new resealing contract, and our expectation is that the quality issues we have experienced in recent years will not continue.

So, to get back to the vexed question, council simply can’t afford, or justify on fairness grounds, a like for-like asphalt replacement on streets where there are low traffic volumes.

A possible solution could be for all of the owners of properties on those streets to agree to pay a targeted rate to cover the extra cost of asphalt. Provided such a rate would not be too administratively complex to apply, that’s something the commissioners could consider.



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