Volume 18, No. 32Journal 32

Velvet Morris Mitchell, Fabricio Leiva Villacorta (Author)

Determination of vehicle wheel wander for urban roadways in Costa Rica

• PDF (Spanish)

The main objective of this project consists in estimate a value of wheel wander representative of Costa Rican roadways, which could be used for pavements design and testing. In order to achieve the objective, wheel wander was measured and computed in 6 different stations with similar characteristics located in national routes from the Great Metropolitan Area of Costa Rica.

Wheel wander is the scatter of vehicles along the length of the lane. Drivers usually follow a normal distribution pattern. In the wheel paths that most drivers follow, traffic load will be higher causing rutting in the pavement. Therefore, in roadways where wheel wander is high, the traffic load is distributed along the lane width, increasing the design life.

For each station only the outer lane, the closest to the camera, was used. These stations are located in National Route 3, National Route 2, National Route 202, National Route 32, National Route 39 and National Route 108.These routes were chosen because of their high truck traffic volume. In each station, a camera was placed roadside. Also lines were drawn covering more than the half of the lane cross section. The position of both heavy and light vehicles was measured.

Standard deviation and confidence interval for variance equations were used to determine the wheel wander. Results show that the mean and 95% confidence interval of wheel wander is drastically higher that the value of 10 cm used by the LanammeUCR for accelerated pavements testing.

Luciano Petit (Author)

Behavioral Interactional Model of Traffic: Diagnostic Algorithm

• PDF (Spanish)

The aim of this article is to present a new theoretical and technical perspective which coordinates knowledge as well as disciplinary, though dissimilar, fields that are necessary and complementary for the analysis and understanding of the complexity of all situations and events relating to transit and road safety. On the one hand, the conceptual principles of Trans-System Transit and Road Safety and the Interactional Behavioural Transit Model are set out; on the other hand, there follows the technical development, in order to obtain a synthesizing point, or points, which will allow us to define such system based on four conditions. The value is obtained using an algorithm that proposes the intersection of lines on a plane of Cartesian axes. It has been run with MATLAB IM software, resulting in graphics which make it possible to diagnose ("path diagnosis") the Trans-System Transit and Road Safety, through the Interactional Behavioural Transit Model, linking physical elements such as road infrastructure, and behaviours such as behaviour in urban drivers.
The theory and the technique result from a fragile interaction between actors (psychosocial environment) and physical elements (physical environment), based on the irreducible structure of their components, and keeping the distinction between such actors and physical elements in a dialectical association of interdependence and integrity that includes dissimilar extremes: Behavioural System and System of Physical Elements.

Fabricio Leiva Villacorta, Edgar Camacho Garita, José Pablo Aguiar Moya (Author)

Simulation of Climatic Variables in Full-Scale Accelerated Pavement Damage Tests

• PDF (Spanish)

Full scale accelerated pavement testing provides much more information about the actual behaviour of pavement structures subject to specific mechanical stresses. While this is the main factor causing damage to pavements, climate also affects performance and has not been extensively studied in full scale tests, much less its effect on an accelerated basis. This article describes part of the implementation of a system to include an accelerated form of weather variables in the laboratory full-scale pavement facility called PAVELAB of LanammeUCR. The system has unique capabilities including simulation of high and low temperatures, wind, rain and solar radiation. Some results of the first tests with the new system are shown in this paper and some of the possible climatic varieties of interest to characterize the climate of Costa Rica in the tests performed in the PAVELAB are also shown.

Jose Corrales Azofeifa, Adrian Ricardo Archilla (Author)

Implementation of a laboratory batching procedure with a correction for fines and moisture

• PDF (Spanish)

The selection of an appropriate aggregate structure is a key step during mix design since this directly affects mix performance and the amount of asphalt in the mix. During conventional batching procedures, the aggregates are dried and sieved into different sizes only to be recombined later into the appropriate proportions to reproduce the design gradation. This type of procedure can produce gradations with substantially larger percent passing the sieve No.200 relative to the target gradation. This paper explores the effects that fines adhered to larger particles have on the batch gradation, the resulting optimum binder content and dust proportion. An improved batching procedure that corrects for fines adhered to larger particles and trapped moisture is presented in detail and shown to replicate the target design gradation more closely. The optimum asphalt content was determined by means of the Superpave® design method for both, a gradation batched conventionally and a gradation batched with the suggested corrected procedure. The results show that the optimum asphalt content and volumetrics obtained in both cases are substantially different. The procedure developed for the fines correction is recommended for routine batching in order to minimize the inclusion of additional fines that can potentially affect the performance characteristics of the mix.

Jonathan Agüero Valverde (Author)

Identifying dangerous routes through safety performance functions: case of Costa Rica

• PDF (Spanish)

Road network screening is fundamental to reduce the frequency and severity of road crashes. For this purpose it is necessary to have a detailed crash database and an updated road inventory, which are not available in Costa Rica. Recently, macro-level crash models have become popular, since their level of aggregation have lower information requirements; they can be used to develop Safety Performance Functions (SPF) at route level. Using these SPFs routes with excess crash frequency can be identified and a detail safety screening can be performed on those routes. This study seeks to identify the most dangerous routes in Costa Rica using the SPFs and the Empirical Bayes method. The results show that the Negative Binomial model is appropriate to represent the SPFs for routes in Costa Rica since it considers the exposure and over-dispersion present in the data. In addition, the model indicates that the most dangerous routes in Costa Rica in terms of excess deaths are the Route 32, followed by Route 2, Route 4, Route 1 and Route 34. The other 5 routes completing the 10 most dangerous are in order Route 35, Route 21, Route 36, Route 27 and Route 6.