# System Proposal for Mass Transit Service Quality Control Based on GPS Data
## 1 Introduction  
In modern societies, mobility plays a significant role in quality of life and is an aspect that has a considerable influence on the socioeconomic development of people. Because of this, we are currently witnessing a large-scale use of transport systems that is giving rise to problems such as environmental degradation, traffic congestion and an increased risk of road accidents. Different local, national and international agencies are constantly producing reports that highlight both the importance of transport systems and the need to address the problems inherent therein. It is estimated that over 40% of the world population spends at least an hour a day travelling by road [1]; the relationship between the rising number of people with heart, respiratory and brain diseases and high levels of pollution has been proven by medical studies [2]; the World Health Organisation [3] estimates that around 3 million people die annually due to outdoor air pollution; and finally, according to statistics, every year 250,000 people in the European Union [4] are seriously injured as a result of traffic accidents, with road fatalities at about 10% of that figure. Transport agencies are tackling these mobility-related problems mainly by, firstly, promulgating traffic rules and regulations that benefit transport and, secondly, using technology to develop more efficient transport systems. A highlight of the latter approach is the use of intelligent transport systems (ITS) to develop public transport systems that are more efficient, environmentally friendly and attract citizens away from the use of private transport. The key element in making a public transport system attractive to citizens is quality, an aspect that means responding to mobility needs and running on schedule. There is general consensus on the aspects that influence public transport users' perception of service quality. These are, mainly, punctuality, real-time availabilityof information on timetables including incidents affecting the service, and shorter waiting times at stops. There are even recommendations and standards, and legislation such as that which exists in the European Union [5], which sets out the parameters to be considered when assessing the quality of service provided by a public transport operator, which include timetable adherence. Because public road passenger transport is affected by external variables such as traffic and weather conditions, user demand, etc., comprehensive quality control in a transport network requires continuous assessment. And this requires elements from the transport network infrastructure, such as sensors, and computer and communications systems, to obtain the required data, which are on a massive scale in the case of medium to large transport networks. This article presents a system for continuously and systematically evaluating the service quality of a public road passenger transport operator. This systematic evaluation is performed using vehicle tracking systems and mobile communications infrastructures used by transport operators, the set-up of which does not require any specific deployment of new devices. In addition, the data provided by the proposed system are integrated into the data model used by the transport operator, thus allowing detailed and continuous analysis of important aspects such as the punctuality or regularity of the services provided to users. In addition to this introductory section, this article is organised into seven sections. The second section reviews related studies, focusing on the criteria, parameters and systems used to measure the quality of service in public transport by road. The third section explains a number of preliminary ideas and concepts to be used in the rest of the article: a general description of the positioning system used by the system (GPS), and a presentation of the conceptual and formal model of the entities involved in evaluating quality of service, as well as the criteria and parameters used.