Traffic management and constructing new infrastructure are the ways in which traffic congestions can be solved. Traffic management comprises of actions such as controlling the speed limit, limited access to heavy weight vehicles, installation of traffic signals etc. Whereas building new infrastructure involves new bridges or underpasses to decongest the sections.
Traffic management, if it works, is the preferred solution for any city engineer because it does not involve new infrastructure cost. Furthermore, these new additions will need regular maintenance. During construction there will be delays and obstruction along the construction site which would lead to longer travel time and longer queues.
3.6.1 Traffic Management
In the study area selected, there is a possibility of installation of traffic signals at two locations: at the Infias roundabout and at the entrance to the Multi Junction node from the Infias roundabout section. As the traffic from all directions tend to flow towards the multi-junction, an experiment showing the effects of installation of traffic signals to facilitate flow to clear the traffic at Infias roundabout.
3.6.2 Solutions Recommended by Municipality of Braga
The Municipality of Braga currently has been working on this situation and have three modified models for the network. All three of them involve construction of infrastructure. Since these models have been suggested after careful surveying by civil engineers, the construction and implementation are sure provided they produce feasible results during the simulation.
3.6.2.1 Alternative 1
Description: The first scenario involves the construction of two sections explained below.
First, a two-way flyover connecting the national highway from the north, N101, until the section just before the Infias roundabout (shown below in blue and green paint).
Second, a diversion from the usual input section in the multi-junction, eliminating the existing section (shown in red paint).
Figure 6: Proposed infrastructure additions Alternative 1
3.6.2.2 Alternative 2
Description: This scenario is the same as the first one with some additions to the infrastructure. The two-lane flyover from the north and the diversion in the remains the same with two other additions.
Firstly, the two-lane flyover takes a diversion to join the exit on the multi-junction towards the east, hence facilitating unobstructed flow of vehicles between the North and East directions (blue and green sections that diverge in two directions).
Secondly, the section coming in from the Infias roundabout into the multi-junction towards the North and East directions (pink sections in the picture below).
Figure 7: Proposed infrastructure additions Alternative 2
3.6.2.3 Alternative 3
Description: This scenario involves the construction of maximum infrastructure and is a bit complicated too. There are 5 major modifications:
The first one is common to all the scenarios, i.e. the diversion from the East coming into the multi-junction (shown in pink).
The second section involves the construction of an extra lane coming from the Infias roundabout into the multi-junction going towards the East direction (shown in red).
Next one is just an addition of a lane in the section coming in from the West joining into the multi-junction (shown in yellow).
Next one is the construction of a flyover bridge connecting the traffic coming from the North joining into the section going to East.
The final addition is the construction of a flyover bridge that connects the traffic input flow from the West with the output towards the North.
3.6.3 Bus priority options
Public transport run by TUB requires prioritization to serve its purpose and combined with traffic signals and detectors, it can be achieved. For example, in the figure shown below, once a TUB bus reaches the detector D, the traffic lights for that section at the Infias roundabout turns green. This serves the purpose of giving way to public transport and also clearing the traffic in front of the schools. But one drawback is that during heavy congestion, the time taken for the bus to reach the detector could take longer.
Nevertheless this solution approach is interesting and worth evaluating.
Figure 9: An example of working of the bus priority traffic management
The main expectation of this approach is to reduce the time taken by the TUB buses to travel the given route in the time that they must. In this project we depict the basic concept of how this works and suggest some ideas of further applications.
3.7 Concluding remarks
Understanding the problems and their causes helps us attain the vision to solve them better. In the next chapter we discuss the solution approach for the problems and model development of the study area in Aimsun simulator. Having understood the causes, we can design some models of our own, even though they won’t be backed up by civil engineers’ approvals, it will be interesting to have a look at the results.
4 CHAPTER 4:MODEL DEVELOPMENT AND VALIDATION
4.1 Chapter overview
This chapter discusses the implementation of the problems and their suggested solutions as discussed in the previous chapter. We look at the step by step solution approach from data collection until the final output comparisons that will be done in chapter 5. Another important section of this chapter is the system validation which will be done by simulating the real-world model and verifying the results obtained with the data collected from site visits which was used in system modelling.