Local bitumen starts to bleed as the mercury rises

The sweltering summer heat is melting roads across New Zealand.

Following a week of blistering temperatures, some road surfaces have reached 60 degrees Celsius, causing the bitumen to ‘‘bleed’’.

Two state highways have started melting in Marlborough but softer roads have also been reported in Wairarapa, Canterbury and Manawatu¯.

NZTA transport system manager Frank Porter said it was unusual to see the bitumen melt at this time of year.

He said there had been melted bitumen on the route between Blenheim and Nelson and also in Marlborough’s Wairau Valley, along the alternate highway to Christchurch.

‘‘We’ve had some areas where the bitumen has started bleeding on State Highway 6, and State Highway 63 [in Marlborough] was particularly bad towards the end of last week.

‘‘It’s not so common this early in the summer, [but] the last week’s run of weather has been quite extreme,’’ Porter said.

Bitumen bleed happened when bitumen below the chip seal melted and rose to the road surface, which increased the risk of skidding.

‘‘Motorists need to be aware the roads could be slightly slippier,’’ Porter said.

‘‘And there’s not that hard chip right up on the surface so when motorists see that black seal they should travel around the corners slower, they should increase their travelling distance behind another vehicle.’’

NZTA had added new chip on some segments of the melted roads in Marlborough, with signs showing where there was bitumen bleed.

NZTA journey manager Lee Wright said if motorists got bitumen on their vehicle, baby oil and kerosene would help clean it.