**2. General Technical Aspects**

To achieve the high efficiency of a BRT system, regardless of new construction or existing mass transit upgrades, several aspects must be taken into account to minimize future interventions. As for any other infrastructure, the design phase represents the central part of the implementation of a public transport system. This is why, before drawing the physical elements of a BRT system, it is necessary to carry out in-depth studies about city urban assets, a demand analysis of potential users, the identification of critical points, analysis of existing mass transit systems, and corridor selection [4,5]. Once the design phase has been concluded, it is possible to begin building and installing the following main elements that characterize a BRT system:


Running lanes represent the main characteristic of BRT systems, for economic reasons. Their construction generally amounts to 50% of infrastructure costs; concerning their asset and dimensions that strongly affect the efficiency of the BRT service, usually the standard width of a BRT runway is 3.5 m, as shown in Figure 1. However, this width is reduced to 3 m to guarantee a lower speed, decreasing accident risks for safety reasons. Regarding the lane's position in a road section, it is preferable to locate them at the edges. In this way, passengers do not need to cross the street to reach the station. This is why lanes are often located in the middle of the road section only when that part of the itinerary is without stops. The construction of barriers at the edges of the lanes is a solution that guarantees only public service vehicles. However, the absence of barriers proves useful when, in the case of accidents or dangerous situations, other vehicles need a recovery place, or to facilitate access to ambulances that need to avoid congested areas. Nevertheless, in that case, the lane must maintain a correct width that allows the presence of more than one vehicle.

**Figure 1.** General Bus Rapid Transit (BRT) corridor section, u.m. = meters.

For these reasons, running lane dimensions are strongly affected by vehicle characteristics that mainly depend on two parameters: size and propulsion. The first is related to driver labor costs per passenger, user comfort, service capacity, and frequency. In contrast, the second has consequences concerning emissions and environmental impact. In lower-demand corridors, it is suggested that large buses are avoided to reduce waiting times for users. It has been noted that typical BRT efficiency is attributed to vehicles, but the operation quality is significantly affected by stations. Such infrastructures may be configurated in several different ways according to their role. Generally, it is possible to distinguish open stations (preferred for stops) or closed stations, and their size depends on lines and user quantity. Stations are positioned in relation to the adjacent urban layout, but the system is optimized if they are close to pedestrian areas due to safety reasons. The processing speed does not depend only on vehicles, stations, or runways, because it is the exchange of information that guarantees a correct and timely operation. Such characteristics relate mainly to two contexts: user information and operators and systems information. The first is fundamental to allow passengers to choose between the BRT system's services concerning their needs. The second one affects the operation of the entire system, so it essential to communicate accidents, vehicles, and route data. The public transport system is equipped with high efficiency IT and electronic telecommunication devices, the so-called intelligent transport systems (ITS), to ensure such capabilities. These devices allow real-time traffic data and communication network control. With regard to technological characteristics, there are several types of traffic light systems, satellite navigators, or speed detectors; moreover, thanks to recent innovations, sensor device systems have been implemented that can be installed both in vehicles and in infrastructure (stations, lanes). Nonetheless, the accuracy and precision of all the decisions in the design phase and concerning the aspects above-mentioned can be complicated to avoid delays at 100%, which for users represent the most significant inconvenience. Such events occur for several reasons, and not always attributable to public transport systems. These depend on variable parameters that are impossible to predict. The case of a BRT system that bases its efficiency on reserved lane intersections represents the most critical point. For safety reasons, BRT vehicles are constrained to operate maneuvers (valid also for non-public transport vehicles) of deceleration, braking, and acceleration, respectively, before, in correspondence, and after the intersection. The aggregation times for such maneuvers create the delay, as shown in Figure 2.

**Figure 2.** Vehicle delay at intersection.

Strategies to manage and maximize such discomfort are various, so the prioritization of BRT vehicles at intersections can be managed passively, with the absence of signal priority and operating according to a pre-defined schedule. Consequently, it is possible to achieve a vehicle detection strategy both in an active and adaptive way with the aim to detect in real-time BRT and traffic vehicles. However, it is commonly preferred to use transit signal priority due to its efficiency. With recent innovations, many other solutions have been studied. One of them consists of implementing an algorithm named TSPAT (Transit Signal Priority for Actuated Timing), which was tested on a real scenario (intersection in Isfahan, Iran) with Verkehr In Städten-SIMulationsmodell (VISSIM) traffic simulation. Such study objects were the "Freiburg intersection" in Isfahan, where there is a BRT station, and in the street, where it is wider, there are two BRT runways positioned at the edges that carry buses in opposite directions. The results of the algorithm above-mentioned showed a more positive trend regarding off-peak hours. For off-peak hours in both for BRT system operation and environmental-economic impact, outputs were all positive. In these cases, delays were reduced by 51% with a reduction in air pollutants and

fuel consumption, respectively, by 6.9% and 6.5%, and average speed increased by 78%. In contrast, peak hours of positive outcomes saw a 21% reduction in delays, the average speed increased by 26%, average fuel consumption increased by 2%, and air pollutants by 2.9% [6]. In conclusion, it has to be underlined that among the several parameters that affect the BRT system configuration, the demand analysis is the most significant. This planning phase provides the number of users, so, according to these data, the BRT system will assume various assets. The BRT configuration solutions referring to the number of passengers are shown in Table 3.


