## 4 Modelled Transport Layers and Traffic Properties  
The proposed architecture is capable of simulating a complex urban transport network with its varied transport layers. In effect, a physical transport layer can be defined as a set of interconnected segments. Figure 6 depicts the seven layers that are modeled by the software agents. These transport layers cover road segments, public transport (bus, trolleybus, metro, tram) segments, bicycle segments, and walking segments. As shown in Figure 6, each mode of transport is represented by agents in a layer, which can interact with a segment of other layers (i.e., a different transport mode). So, an agent is connected to agents of the same type (i.e., same transport mode) and agents of other types (i.e., different transport mode) to enable multimodal collaboration. Each segment in the transport layer has static and dynamic characteristics. The static characteristics define the physical aspects of the segments, such as the length, Global Positioning System (i.e., GPS) coordinates, and number of lanes. However, the dynamic characteristics refer to traffic stream properties (e.g., flow, speed) that change over time based on the data received from the road sensors and SCOOT system [69]. During the route recommendation, the system considers the capacity of the modes of transport with the aim of balancing between the use of the network on the one hand and the demands of the commuters on the other hand. Table 3 summarizes the specific characteristics of the transport network that our system models when attempting to provide the fastest or eco-friendliest route guidance. The static characteristics of transport are properties of the physical transport network and are thus extracted from the Open Street Map (i.e., OSM). These properties are generally not linked to the behavior of travelers. Practically, for each segment in the network layer, the system collects static (e.g., length of road lanes, number of lanes, segment location) transport information. Figure 6: Interconnected layers of transport segments. Various agent types are used to model the traffic network, where each agent, referred to as a transport agent in our study, can be used to simulate one type of transport mode, e.g., buses, trolleybuses, metros, trams, bicycles, and walking. The transport map is divided into interconnected segments where each software agent simulates a single transport link instead of the whole roads. Consequently, multiple transport network layers are created (e.g., road network, bus network, and so on) by the system. The agents hold different static and dynamic information about the traffic. Despite their differences, these agents interact and collaborate to assist in the creation of the most appropriate multimodal route while considering user preferences and traffic conditions. Figure 7 highlights the exact properties of each agent while simulating various transport modes. Every agent will aim to keep commuters' demands within the capacity of the segment it models. Next, the system models the dynamic (average speed, travel time, carbon emissions) traffic characteristics, which are obtained from the SCOOT system [69] and the traffic data estimator on a regular basis. We are estimating the carbon emissions for each transport segment based on the traffic patterns extracted from the historical and current congestion data. The historical data were collected the from the SCOOT system and roadway sensors.