Resources

Responses to a discussion document on the development of the Road Assessment and Maintenance Management (RAMM) system, issued by Transit New Zealand in 1995, are summarised. Conclusions are drawn from the information in the discussion document and from the responses. Recommendations are made for development of the RAMM system covering the scope, objectives and functionality of the system, developments that should be undertaken, the involvement of Transit New Zealand, Transfund and other agents, financial assistance and research needs. Keywords: Activity management, information system, maintenance management, pavement management, RAMM system, road management

A literature review was carried out in 1993 on the potential use of crumb-sized ground tyre rubber (GTR), obtained from recycling waste tyres, as an additive to bitumen used in constructing New Zealand pavements. GTR, also called crumb rubber, has been used either mixed with bitumen or incorporated as part of the aggregate fraction in hot asphalt mixes. The expected cost of the GTR and the cost of specialised blending and spraying equipment would make bitumen-rubber blends more expensive to use as a chipseal binder than the synthetic rubber being used in 1993 in New Zealand pavements. GTR could possibly be used in hot asphalt mixes where it would be expected to increase pavement flexibility at low temperatures. Insufficient information was available to make a benefit/cost analysis of its use under typical New Zealand pavement construction conditions. Keywords: Tyres, environment, disposal, roads, pavements, bitumen, binders, asphalts, New Zealand

Providing a safe, comfortable, cost-effective visual environment to help drivers navigate rural roads requires a better understanding of the strengths and limitations of different delineation devices, materials and treatment configurations. An international literature review examined different options to test on low-volume rural New Zealand road settings, and an expert panel prioritised four of these options to be trialled.  

Four on-road trials were run to examine delineation configurations and materials that could provide better value for rural roads. The key aspects to deciding treatments were to do with targeted delineation (to assist drivers in intuitively signalling more difficult parts of the road network), consolidation (where one configuration with a new product might replace two traditional products), and better delineation in rain, which is arguably a common poor visibility environment (where crashes are over represented).

Research into moisture in pavements in New Zealand started in 1979 and led to the instrumentation and monitoring of moisture in two sample pavements. The project recorded in this report was commissioned in 1995 to indicated the future directions that New Zealand research should take to evaluate moisture conditions in pavements. Fundamental studies in New Zealand should not be commissioned until the results of long-term projects underway in the US become available. These projects are researching the long-term effects of seasonal changes of moisture on the strength and performance of pavements. Instead, research during pavement operations is recommended and should:

Determine the effects of a range of pavement parameters on the theoretical distribution of moisture in pavements by performing a sensitivity analysis to select suitable sites.

Data consisting of levels of scabbing (chip loss) of rating sections of New Zealand state highway chipseals, together with a seal stress classification calculated from the road geometry, were collected and analysed to look for relationships between seal type, seal stress classification and susceptibility to scabbing. The data indicates that there is no evidence of seal designers adjusting the seal type to accommodate for high stress sites. There is a clear hierarchy of seal types as regards susceptibility to scabbing, but no relationship could be found for the proposed stress classification system. Keywords: Chipseal, scabbing, ravelling

This project involved market research among motorists in New Zealand to establish unit behavioural values of travel time savings under a range of conditions, for application in the evaluation of transport projects. Interviews involved a series of 'stated choice' games, in which respondents chose between a recent (reference) trip as car driver and two alternative trips, which differed in terms of various trip attributes (total travel time, degree of congestion, uncertainty of arrival time, fuel costs and toll charges). A series of multinomial logit models was estimated to identify the value of each trip attribute. Unit values of travel time savings for car drivers in a range of conditions were derived, in particular according to trip length and purpose, degree of congestion, and uncertainty of arrival time. The values derived were compared against those currently used for project evaluation purposes and recommendations were made.

Horizontal curves have been recognised as a significant safety issue for many years, a more important factor than road width, vertical clearance or sight distance. This study investigates the issue of speed selection through curves from several different perspectives. The relationship between safety and curve speed in New Zealand was analysed using data from the Ministry of Transport’s Crash Analysis System (CAS) database. A sample of curves was selected and surveyed. Following this, a method for determining the appropriate safe curve speed for different vehicles was developed based on the vehicle performance characteristics. In parallel, a driving simulator was used to investigate the effect of different warning sign and road marking treatments on drivers’ curve speed selection and lateral positioning.

Coal tar-derived roading material contains over 1000 times more polycyclic aromatic hydrocarbons (PAHs) than equivalent bitumen pavements and has been identified as a major source of PAHs in both Christchurch and Auckland aquatic receiving environments. Many old streets containing coal tar will soon require reconstruction, and therefore the excavation and potential disposal of contaminated road construction layers represents a significant financial and environmental problem. To address this problem, we evaluated in-situ foamed bitumen (FB)/cement stabilisation as an environmental acceptable method to reuse the contaminated tar road material. Based on contaminant leaching and toxicity, the reuse of tar-contaminated roads as compacted stabilised base material represents minimal risk to the environment. FB decreased PAH leachate concentrations by ca 4–6, although algal toxicity was correlated to leachate copper, which was increased by the co-use of alkaline hydraulic binders.

Subgrade stabilisation is a common road construction practice in New Zealand. Stabilisation results in increased subgrade strength and stiffness, and provides a stable platform for the construction of the overlying pavement. It also provides protection of the original subgrade from stresses generated by wheel loads passing over the pavement surface. This project carried out in 1998 has examined the performance of lime-stabilised subgrade materials using both laboratory and field investigations for three test pavements. The field investigations have shown that the enhanced strength and stiffness characteristics of stabilised subgrade materials can be relied upon for periods of twenty years or more. Laboratory investigations have been used to examine correlations between the elastic modulus of lime-treated and untreated soils and other basic test methods. Good correlations have been established between the CBR and both unconfined compressive strength and split tensile strength, for the silty clay soil used in the investigation.

Geosynthetic-reinforced soils (GRS) have been found to be cost-effective compared to traditionally used retaining structures in specific situations. As a consequence the application of GRS to structures carrying roads and/or pedestrian traffic is rapidly increasing. Also GRS structures are less prone to damage under seismic loads than conventional type structures. GRS is a comparatively new technique and the desgin methods for GRS are not well established. As a result, New Zealand geotechnical engineers currently use several different overseas standards and design guidelines to design GRS structures. Therefore research was undertaken to prepare guidelines for design and construction of GRS structures in New Zealand.  Stage 1, undertaken in 1997–1998, has been published as a review and discussion paper in 1998.  The result of stage 2 is this draft of comprehensive guidelines for design and constuction of GRS structures, both walls and slopes, in New Zealand.