The high-speed bus corridors or BRT currently in operation are mainly based on central bus lane system (Alternate Option) and are integrated with the road networks and intersections there on with various alternatives as are appropriate and feasible. A set of at grade intersection alternatives and pedestrian crossings are suggested in guidelines [07] for BRT corridors, with a central bus lane system, in Indian cities, some of which can also be adopted in a BRT system with curbside bus lanes with modifications appropriate for the system.
The concept – a grade separated intersection – integrated with curbside bus lanes (Base Option) and neighbouring intersections with a split grade separation arrangement is detailed hereinafter. As indicated earlier, traffic movement through the intersection is segregated by size of vehicles with bus movements on surface at (G 0) and all SMV movements through underpasses at (G -1) and (G -2) levels.
The service roads, on the northern and southern sides, on both the legs of the intersecting road, and; those running along arterial road, are connected by rotaries and underpasses below the elevated bus stops and bus lanes for north-south-north transfer of SMVs. The split-flyover arrangement is suggested to maintain signal free LI-LO of bus movements also. The LI-LO bus movement is signal free due to absence of conflicting pedestrian movement in their paths.
Pedestrians and bicycles cross, under the elevated bus lanes, at grade, on sub-arterial, from one side of the service road to the other. This crossing also provides a continuous path for bicyclists moving along the arterial although with a semi-circular detour on their path. But, the same detour also provides connectivity to the bicycle lanes on the other side of the sub-arterial road. Pedestrian movement between elevated bus stops and pedestrian bridges will be during the dwell times of buses at the bus stops controlled by a two-phase signalling system.
Passengers access the elevated bus stops through connecting ramps with the pedestrian crossings on the sub-arterial road. The combined pedestrian and bicycle crossing to have a split arrangement for pedestrian movement with bicycle movement in the centre. This arrangement allows non-passenger pedestrians to use the pedestrian path, on the other side of the ramps landing, without being hindered by the passenger movements.
Buses change grade linearly and not on a curvilinear ramp. So, do SMVs. As the ramps run along the path. In both the cases – buses and SMVs – turns take place on reaching a new grade exclusively for the requisite manoeuvers as in the case of SMVs or the requisite manoeuvers in the case of buses take place before or after halting at the bus stops according to route plan.
The placing of the bus stops at the mouth of the arterial and sub-arterial intersections – at grade or elevated as appropriate – allows provision of a mid-block bus stop resulting in an overall inter bus stop spacing of 300 meters with a spacing of 600 meters between arterial and sub-arterial road(s). That means, a bus stop is within 150 meters from any point on the arterial road and is perceived by bus passengers to be closer than that. That is because bus passengers consider the start of the bus stop in their direction of approach to be where the bus stop is located rather than the centre of the bus stop. This is also true in the case of bus stops on the sub-arterial road. A mid-block at grade bus stop, between the two bus stops on either end, on the sub-arterial, may be placed along the minor road and close to the mouth of the intersection with a Left-In / Left-Out arrangement.
With a Left-In / Left-Out arrangement for all vehicles on both sides of the sub-arterial, vehicles from the minor road intending to turn right or access areas on the other side of the sub-arterial need to take a U-Turn at respective end-intersections, approximately 300 meters away, post Left-Out for the purpose. Similarly, vehicles moving along the sub-arterial need to take a U-Turn at the approaching intersection to access areas on the right side.
An appropriate mode wise – bus, SMV and pedestrian – signalling system may be considered to control the flow of the traffic through the rotary intersection of sub-arterials. Weaving conflicts of buses and SMVs may be minimised or eliminated with bus priority lagged-phase for vehicles or separate phases for each of these modes in the signalling system. That is, in the former, buses are allowed to enter the rotary first and followed by SMVs.
The space under the bus stop on arterial/sub-arterial intersection may be used as bike parking area to encourage public
It may be appropriate to shift the road side mini bus-terminals, common in India, on arterial and sub-arterial roads, to the centroid or there about of the area enveloped by the arterial / sub-arterial road network, to reduce the congestion on arterial network. This distributes boarding and alighting loads at the arterial road side bus stops minimising their sizes and also the bus stop access distance to bus users in the areas encouraging the use of public transport.
Integration of bus stops at the mouth of intersections on a road network is conceptually feasible with curbside bus lanes. Three different forms of integration were examined here. The bus movement through the intersection in two of them is segregated from SMVs which move through the intersection at a different grade. In one of these forms (Form-1) of integration, buses move through the intersection at (G 0) level and in the other (Form-2) move at (G +1) level with bus stops located at the same level of their movement. In the third form, (Form-3) of integration, bus stops are at level (G 0) with buses and SMVs moving at the same level and their movement through the intersection is segregated by mode wise phases in the signalling system. The concepts are developed to minimise the effort pedestrians exert to cross an intersection. In Forms – 1 & 3 pedestrians cross an intersection at (G 0) level requiring no additional effort than that is normal for such an activity. In Form-1, pedestrians cross the intersection during dwell time of buses eliminating conflict between the two and in Form-3 pedestrians cross during a dedicated phase in the signalling system. In Form-2 some additional effort is required as the pedestrian crossing involves an elevated facility for the purpose. However, the effort would be less than that in the elevated pedestrian facilities currently in use. For, the concept considers elevated pedestrian facility with a 3.5 meters MVC unlike the current practice of 5.5 meters MVC as only SMVs pass under. In this option (Form-2), transit passengers, moving between bus stops, can cross at the same level (G +1) as the pedestrian crossing across the arterial road is integrated at the same level as bus stops. Also, pedestrians who need to cross the arterial road or passengers accessing the bus stop cross the service road only and not the entire width of the sub-arterial.
The rectangular blocks, enveloping the concept interchanges, in Form-1 (~6 ha) and Form-2 (~5 ha) are slightly larger than the area occupied by conventional interchanges such as a Trumpet Interchange (~4.4 ha) and Full Cloverleaf (~4.9 ha) [05]. The concept interchanges, in Form-1 (~2.9 ha) and Form-2 (~3.2 ha) occupy a small part of the blocks suggesting that the concept grade separation alternatives, the unconventional ones, could be designed in an area smaller than that required for the regular interchanges.
References:
00 Interchange (road) - Wikipedia, the free encyclopedia
01 Marco, Guerrieri et al. (2013). An International Review on One and Two Level Innovative Unconventional Intersection and Interchange. ARPN Journal of Engineering and Applied Sciences
02 Gidugu, Varadaraj. (2014). Optimal Allocation of Road Space (OARS) – A Concept. Research Gate
03 IRC:86-1983 - Geometric Design Standards for Urban Roads in Plains
04 IRC:3-1983 - Dimensions and Weights of Road Design Vehicles
05 IRC: SP:90-2010 Manual for Grade Separators & Elevated Structures
06 Bus Rapid Transit Planning Guide June 2007
07 EMBARQ: Draft - Road Safety Design Guidelines for Bus Rapid Transit in Indian Cities
08 URDPFI Guidelines Volume-1 2015
09 IRC: SP:84-2014 Manual of Specifications & Standards for Four Lanning of Highways through Public Private Partnership
10 MOUD, GOI: Recommendatory Urban Bus Specifications – II April 2013
11 Premier Road Carriers Ltd – Road Cargo Transportation in India
12 Michigan Left (MUT)
13 FHWA - Access Management in the Vicinity of Intersections
14 IRC:92-1985 – Guidelines for the Design of Interchanges in Urban Areas
15 Tomaz Tollazi et al. (2015). Environmental, functional and economic criteria for comparing “target roundabouts” with one- or two-level roundabout intersections. Research Gate
16 IRC:103-1988 – Guidelines for Pedestrian Facilities
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