20.2 Pavement Features

Pavement features include aspects such as utility covers, pavement markings, and different surface treatments. Each can present a particular challenge for motorcyclists as the materials can often have a different and lower skid resistance to the surrounding roadway. A difference in surface materials and skid resistance can result in a motorcyclist losing control particularly if the feature is located in an area that requires motorcyclists to brake or turn. This issue can be further compounded in wet conditions.
The following features and potential design considerations are considered in more detail within this section:
  • Metal covers;
  • High friction surfacing;
  • Removal of pavement markings; and
  • Pavement markings.

20.2.1 Metal Covers

Motorcyclists are vulnerable to skidding on metal covers which typically have a lower skid resistance than the surrounding pavement. Where there is a sudden change in road surface properties, it can lead to stability issues for motorcyclists.
The locations that are most problematic are where a cover is located within the riding line in areas where a motorcyclist is likely to brake, turn, accelerate and/or change lanes. This can be a particular issue on curves, intersections, and roundabouts.
Treatment
: Historically, metal covers for utilities and storm drainage have been located within the pavement. However, designers should strive to ensure that metal covers are not designed for new pavements, including main lanes, shoulders, turn lanes, and median openings of high speed and/or arterial roadways. If these facilities already exist in the pavement, they should be relocated where practicable.
Where there are existing metal covers that cannot be practically moved, then they should be treated with a surface or coating so that the polished skid resistance value (PSRV) matches the surrounding pavement.
Details for metal coverings should also be reviewed to ensure that the tops are flush with the adjacent pavement and do not present a height differential.

20.2.2 High Friction Surfacing

High friction surface treatment (HFST) provides an enhanced level of skid-resistance and is typically applied on high speed roadways, the approaches to signalized intersections, roundabouts, small radius curves, and pedestrian crossings.
Where there is a transition from a HFST to a standard road surface, motorcyclists will experience a reduction in grip between the tires and the pavement. This may not be a problem on straight sections of pavement but, if the HFST ends on a bend, a change in the road surface friction can destabilize a motorcyclist.
Where HFST is terminated is based partly on engineering judgement, therefore it is important that the surfacing extends to a point where the hazard has diminished. An example of this is on the exit from a horizontal curve where the extension of the HFST by a matter of feet can move the transition point beyond the bend and onto a straight section of pavement.
This can be a simple but effective measure to assist motorcyclists.
Treatment
: Designers need to specify appropriate friction characteristics for pavement surfacing depending on the nature of the road environment at each location. This includes where motorcyclists and other road users are accelerating, braking, and cornering.
HFST may be recommended in the following scenarios:
  • Approaches to and across intersections, approaches to roundabouts and traffic signals;
  • Approaches to pedestrian crossings and other high-risk situations;
  • Gradients greater than 5% and longer than 150-ft; and
  • Horizontal curves on high speed roadways with the minimum radius at normal crown and near or at the minimum radius for full superelevation, where the side forces are at their highest.

20.2.3 Removal of Pavement Markings

As highway layouts change, pavement markings are repeatedly renewed, or surface dressing is applied over old markings. This can lead to an accumulation of pavement markings and surface treatments which can destabilize motorcyclists particularly if this results in standing water. Similarly, masking of redundant markings can also result in areas of surfacing with different skidding resistance.
Treatment
: When placing new pavement markings, it is best practice to remove the existing pavement markings entirely to eliminate the risk of a build-up of material. When grinding is used to remove existing markings, the grinding should be specified in such a way that the ground pavement surface does not appear to still be pavement markings in wet or dark conditions.

20.2.4 Pavement Markings

Pavement markings may have lower skid resistance than the pavement surface, which may impact motorcyclists or bicyclists more than vehicles with 3 or more wheels. Larger marking area, such as crosswalks and stop bars, may pose even greater issues.
Treatment
: When introducing pavement markings, it is good practice to locate them away from where motorcyclists are likely to be accelerating, braking or turning. Pavement markings with an improved skid resistance similar to that of the adjacent roadway could be used where the road marking is considered necessary.
If thermoplastic markings are used, designers should check the specifications to ensure that a sufficient quantity of glass beads or some other rough surface additive are included to provide some skid resistance in wet weather as well as maximizing reflectivity.
A designer may also investigate manufactured roadway striping that is adhered to the pavement surface and can be specified with high-friction surfaces that are resistant to wear.
There are some disadvantages around application of Methyl Methacrylate (MMA), including ‘greying’ of the marking over time due to traffic and the retroreflective performance. Designers need to take a balanced approach when considering pavement markings and use different types of road marking dependent on the site and the potential skidding risk to motorcyclists.