The Idiots' Guide to Highways Maintenance
Copyright © 2000/08, C.J.Summers

It is always wise to check the temperature of delivered bituminous material, before laying if possible.
This is not always possible with modern health and safety legislation, but it certainly should be performed as the lorry tips into the hopper of the paver.
Overheating at the time of production and during storage is one of the major causes of poor performance of bituminous road surfacing materials, and can reduce the life of the road surface considerably. Overheating is also quite likely to render any polymer modifier inert, so not not providing any improvement to the bituminous mixture that was intended. 
Ways of testing for the performance of polymer modifiers are found in the Specification for Highway Works (SHW), Volume 1.
Specified temperatures for mixing and storage of bituminous mixtures were able to be found in BS 594, until the 1st. January 2008, when this standard was superseded by, 
BS EN 13108-4 : 2006 : Bituminous mixtures - Material specifications - Part 4 : Hot Rolled Asphalt
and,
BS 594987:2007:Asphalts for roads and other paved areas -
Specifications for transport, laying and compaction and type testing protocols
The presence of large amounts of fumes as the lorry tips is an indication that the material may be overheated, check the temperature.
This particular load was in specification at approximately 170°C (50pen. HRA surface course has a maximum temperature of 190°C) and what you can see is steam as the water from the rollers evaporates.

 

The height of the tamping/vibrating "bed" at the back of the paver is now controlled by hydraulic rams, but many years ago it was actually controlled by a coarse threaded screw mechanism, and to this day the operator who controls the height of the "bed" is known as the "screwman".
The driver will operate the augers that supply the the bituminous material from the centre of the machine out to the edges of the mat so that the amount of material along the length of the bed is constant. Fluctuating amounts of material at the "bed" and along the "bed" can cause the bed to raise and lower hence producing a poor ride quality. 

Here the "screwman" is checking the thickness of the laid mat by pushing a sharp probe (usually a screwdriver) through the laid material to existing hard road surface below, marking it with his thumb and then measuring it against a rule, isn't technology wonderful. Of course any supervising person can also perform this simple task to ensure correct thickness of material is being laid, but be aware thickness tolerance is allowed in the Specification for Highway Works (SHW). If you are paying for work on a square metre basis rather than tonnage it is not uncommon for laid thickness to be less than the nominal thickness specified, but may well be within the specified tolerance.

Precoated chippings being laid on to the already laid hot rolled asphalt (HRA) wearing course. The majority of criticism laid at HRA and precoat chippings as a road surface is a result of poorly maintained "chipping spreaders" and short staffed or  inexperienced chipping gangs operating them.
There is nothing at all wrong with the hot rolled asphalt and applied precoat process, it produces first class road surfaces that are very long lived, skid resistant and makes optimum use of scarce (and costly) high specification aggregate.
It is always wise to check that the chipping spreader works correctly, and that the rate of spread of chippings is set correctly, and uniformly across the mat, before you start laying the hot rolled asphalt.
If you have started to lay the asphalt, perhaps 20 to 30 metres, before you commence using the chipping spreader and then find it is not working correctly. You are then you are already in trouble because the asphalt waiting to receive chippings is already cooling, and who knows how long it is going to be before the chipper is working properly.

The chippings must be rolled in to the HRA layer as soon as possible after laying, in order that the precoats become securely attached to the surface. This is because it is necessary for the binder coating around the chipping to melt and fuse with the bitumen in the asphalt so that a firm complete physical bond is formed between the asphalt and the chipping when the new road surface cools to ambient temperature.
Note the "3-point" roller is reversing onto the newly laid mat and precoated chippings, this way maximum compactive effort it applied, i.e. the greatest weight spread over the smallest area of roller.
Be careful of wind chill, high winds on a day of "moderate" temperature can cause more cooling of the asphalt surface than cold temperatures on a still day.
It is good practice to not allow the paver to advance any faster than the chipping spreader can follow.
If the asphalt surface chills before the chipping is applied to the surface, there will not be sufficient heat to melt the precoated binder layer on the chipping thus ensuring a positive bond between asphalt and chipping.
In the worst case scenarios the chipping is seen to sit in a "depression" in the asphalt without any asphalt surrounding it, these chippings are quickly lost.