Bleeding roads: NZTA keeping a close eye on highways in heat

A truck and trailer stuck on Morere Hill last Friday, due to bleeding tar. Picture supplied

The region’s highways are being closely monitored after a spike in  temperatures saw a host of areas experience melting roads.

Late last week motorists took to social media to express concerns.

One person who drove their van around Manutuke said they spent nearly an hour to clean the tar off it.

“It was like someone had flicked it with a black paintbrush.”

Another motorist posted, “It was seriously sticky on Morere Hill. Quick thinking is the only way we got past the three trucks stuck.”

Another said the melting tar ”was like a river” around Matawai.

Some also expressed concern given the weather had not been particularly hot.

Responding to The Gisborne Herald, NZ Transport Agency Waka Kotahi acting maintenance and operations regional manager Mark Owen pointed out road surface temperatures are typically significantly hotter than the air temperature since the road surface retains the sun’s heat for a lot longer.

“For example, when the air temperature reaches the high 20s or early 30s, the temperature of the road may reach 55 degrees or higher,” he said.

“NZ Transport Agency Waka Kotahi is aware that roads in the region have shown signs of ‘bleeding seal’ or sticky surfaces over the past few days in particular. Bleeding seal isn’t an East Coast-specific occurrence.

“The first onset of hot weather in a season can create issues with newly constructed chip seals especially on uphill inclines, but settles down as we move through the summer.  Even some older seals can ‘liven’ up with the first flush of hot weather. Saturated road surfaces can sometimes also exacerbate bleeding seal as water is released from the road.

“Short-term management of bleeding can include things like water spraying to reduce temperature, application of additional sealing chip to the surface, or speed restrictions.  Longer term, the site might require water cutting or resurfacing, or for older sections of road if the damage/deterioration is severe enough, reconstruction of the road surface.

“Bleeding seal in recent days will be closely monitored with chip spreaders on standby in Wairoa district and in Hawke’s Bay,” Mr Owen said.

As well, a water cart was on standby. Crews would be monitoring the network both pro-actively and by responding to any concerns raised through the 0800 4 HIGHWAYS number.

“A water cart and chip spreader have been used on previous occasions to successfully address bleeding seal.”

All bitumen is imported into New Zealand from overseas refineries.

“It continues to meet the same standards as specified by Waka Kotahi,” Mr Owen said.

“NZTA sets out bitumen specification for use on road surfaces and covers the likes of the approval process required prior to importation and minimum characteristics for bitumens imported.”