## 7 Improvement of the Runway Management System  
The primary objective of this review was to determine improvements in runway friction, texture and aircraft skid resistance management for reduced aircraft skidding risk. Current friction assessment, runway maintenance, and surface condition reporting systems provide a reliable tool that can provide safety for aircraft and passengers. However, in this review it was found that the current ICAO friction assessment and skid resistance management system contains some elements that could be improved in the future. These include the following:  
* There is no standard method or protocol for the determination of a characteristic value of macrotexture from multiple sand patch of other macrotexture measurements;
* There is no standard method or protocol for the determination of characteristic values of CFME wet friction from a CFME survey;* The frequency of CFME surveys does not include a minimum frequency for regional airports with a low frequency of jet aircraft or airports with turboprop aircraft operations only, with many tested annually or when rubber contamination is visually identified;
* CFME-measured friction is significantly affected by temperature, meaning annual measurements are not necessarily representative of the annual cycle of friction;
* CFME measurements are not directly relatable to aircraft braking performance calculations because of the significant differences in vehicle speed, test wheel normal load and tire pressure of the CFME, compared to a typical aircraft;
* GRF does not allow adjustment of the RWYCC to intermediate friction levels;
* Microtexture is important, in combination with macrotexture, for aircraft skid resistance on wet runways, but microtexture is not routinely measured, due to historical equipment limitations, although new equipment and methods are now available, albeit some of these are time consuming and limited to laboratory use;
* Volumetric texture can be measured by contact methods (including deep pores and interconnected voids) and non-contact methods (excluding deep pores and interconnected voids) providing two important, but distinctly different, characteristics, making attempts to identify a universal conversion between the two impossible. Some of these weaknesses could combine together or with other circumstances to lead to aircraft accidents, such as the Fokker F100 overrun at Newman Airport [54]. In this example, the runway friction levels were between the maintenance and minimum levels. Technically, that meant that no additional information about surface conditions was required to be reported to pilots. However, the actual surface friction of the wet runway surface was not provided. The historical friction survey results were likely affected by the annual variations in the measured friction levels as well, which led to an overestimation of aircraft braking capability. When combined with standing water in the wheel paths (Figure 7), and an extreme weather event, the runway overrun occurred. Another example is the Boeing 737-8 FE overrun at Hobart airports, and this highlights the necessity of reliable and early microtexture assessment [175]. Potential elements of an improved friction assessment scheme have been developed and are presented in Figure 31, where arrows represent friction assessment and interpretation steps. In international practice, during the report of friction for landing and maintenance (\(\mu_{\text{reported}}\)), two steps are presented. First, the actual friction level (\(\mu_{0}\)) is assessed using CFME testing. This step is affected by weather conditions, equipment, and operator effects. This means that test results (\(\mu_{\text{tested}}\)) contain an inevitable error. Next, the assessment results are interpreted in terms of maintenance requirements and landing restrictions.