Resources

A research project was undertaken to appraise international evidence on the effects of changes in urban public transport systems and services on the extent of switching to/from car travel and on total road traffic volumes, and to develop guidelines for use in the evaluation of urban transport projects in New Zealand. The major part of the project involved collection and appraisal of international evidence, for situations where changes have been made to the urban public transport system, on the proportion of additional public transport trips that would otherwise be car driver trips, and on the effects of the mode switching on overall road traffic volumes. Evidence was collected mainly from Europe, USA and Australia and appraised by type of public transport change, ie. major new corridor projects, service enhancements, fare changes and on-road priority projects.

Precast pre-tensioned concrete bridge construction became common in New Zealand in the 1950s and a large number of pre-tensioned concrete bridges were constructed between 1953 and 1980. These bridges do not meet today’s durability requirements and many are at risk of chloride-induced pre-tensioned reinforcement corrosion. This deterioration can be difficult to detect in visual inspections and has immediate structural implications, so prediction or early detection of at-risk structures is critical for bridges to achieve their required service lives. This report presents an assessment of the New Zealand pre-tensioned concrete bridge stock and identifies bridges at risk of pre-tensioned reinforcement corrosion. Construction eras based on evolving construction practices are identified, and examples of typical beam types used in each era are presented. The exposure classification of each pre-tensioned concrete bridge on the state highway network was remotely estimated using a Google Earth-based tool developed for the purpose.

Geotextiles are permeable textile fabrics used in engineering applications. This report is a review of geotextiles and their uses in pavements of both sealed and unsealed roads. Also reviewed is the use of geotextiles for filtration and sub-surface drainage. Most of the readily available geotextiles are of either woven or non-woven construction using synthetic fibres. The types of synthetic geotextiles and their generalised porperties are described. Specific properties are given for the geotextiles currently available in New Zealand. The test methods used to measure a geotextile's general, mechanical, hydraulic and durability properties are commented on. The four main functions a geotextile can perform are separation, filtration, reinforcement and drainage. The function or funtions a geotextile performs in any specific application depends both on the situation and on the geotextile. Understanding of the function(s) performed in each of the many situations covered is essential for proper geotextile selection and usage.

The reproducibility and repeatability of the sand circle test for measuring texture depth in pavement surfaces was compared with a new test using wallpaper size and a flexible perspex plate covered by a rubber pad. The new test was found to be more precise. Keywords: sand circle, texture depth, Transit New Zealand stationary laser profilometer, repeatability, reproducibility, alternative test, wallpaper size

This report describes work to investigate sealing aggregate bonding to standard and polymer modified bituminous binders. The work included investigation of the variation of adhesion strength for different aggregate surfaces, the effect of water on binder-aggregate bonding, and development of a test for measuring binder spreading rate on plane surfaces. The spreading rate test was generalised to rough surfaces, and results fitted to power law equations for degree of spreading. This test has the potential to become a standard method for evaluating aggregate-binder adhesion, but further work with various aggregate surfaces and comparison with field-trial results is needed to achieve this. Keywords: adhesion, aggregate, bitumen, chipseals, polymer, modified binders, roads, wetting

A research study was undertaken, in 2001–02, for New Zealand and in other countries, of the temporal spreading of traffic peaks, or 'peak spreading', on roads in urban areas. The objectives of the study are to:

review available evidence of, and research into, traffic peak spreading obtained from cities in New Zealand and elsewhere
examine the effect of traffic peak spreading on modelling and evaluation. The two major purposes of the report are to:

describe the phenomenon of peak spreading, why it happens, why it is important, and where it has been observed in the world;
assess how peak spreading, given its importance, has been incorporated in new scheme appraisals by various governments and how it has been represented in modelling and evaluation. Recommendations for incorporating peak spreading as an integral part of transport planning are made.

The objectives of this project, undertaken 2005/6, were to:

review the international technical literature on the topic of environmental issues relating to the use of waste and industrial by-products in road construction applications, and
recommend a set of guidelines to allow road controlling authorities and environmental agencies to determine if various waste or environmental by-products are appropriate for use in road construction. The international literature shows that the topic of environmental impact is extremely complex and, by necessity, any assessment strategy needs to be relatively conservative for it to be practical, cost effective and reliable. The study has shown that a number of documents that address the issues of hazardous substances and acceptance criteria for contaminants are currently available in New Zealand. A new assessment process has been suggested as a result of the literature review.

A study of cores from multilayer chipseals shows that fine solid materials (passing 4. 75 mm) fill a significant proportion of the chipseal volume that would otherwise be available for bitumen. If fines are ignored, the available voids are typically about twice the expected volume of bitumen that would be sprayed. Generation of fines may therefore contribute significantly to premature flushing. The origin of these fine materials remains to be examined; at least six different processes may contribute, and the relative contributions may vary from site to site.

The majority of fatal and serious crashes in New Zealand occur on rural two-lane roads. Data on historic crash patterns is not always sufficient to enable a suitable diagnosis of the safety deficiencies of various sections of this rural road network. It also cannot readily identify safety issues on low-volume roads and shorter sections of highway, where the relative scarcity of crashes may mask the considerable potential for safety improvements. This pilot study covers the second stage of a three-stage research project that aims to quantify the impact of all key road features on the safety of two-lane rural roads. This stage of the study involved the collection of road alignment, roadside environment, traffic flow, and crash data for 200 sections of rural road, each one 400m long, throughout the Waikato region of New Zealand.

The design of concrete beams for shear loading is governed in New Zealand by the provisions of NZS 3101. The shear design provisions of NZS 3101 impose two limits on the permissible design shear capacity, including a maximum shear capacity of 8MPa. This 8MPa limit influences the efficiency of concrete beam design, and in particular the design of concrete bridge beams that have concrete compressive strengths greater than 40MPa. The validity of this limit was assessed through an examination of a number of other international design standards, statistical analyses using databases composed of all previous experimental testing of reinforced concrete (RC) and prestressed concrete (PC) beams, and results from an experimental investigation aimed at addressing deficiencies in the compiled databases. The research found that the limits in NZS 3101 are excessively conservative compared with the limits imposed in most other design standards.