DOUBLE DECKER BUSES IN – RETROFITTING A CITY Fiona Tang and Remi Cruz (Auckland Transport)

Abstract

To increase capacity on high demand bus routes and accommodate increasing public transport patronage, double decker buses are being rolled out in Auckland. As larger framed buses introduce new areas of risk to the road network, Auckland Transport (AT) assessed key bus routes and identified obstacles that required modification or removal to allow the safe passage of double decker buses.

With no clear guidelines on the safe corridor envelope, AT worked from first principles and introduced new techniques. A measuring device that enables cost effective data capture was developed. To understand the effects of extreme bus manoeuvres on the front and tail swings, a trial road was built to simulate a double decker bus approaching and leaving a bus stop.

This paper also discusses the challenges of retrofitting an existing road network involving multiple challenges and multiple stakeholders in addition to legal, environmental, and operational constraints to achieve the primary objective of providing safe corridors for double decker buses in Auckland.

Key Words

Auckland Transport, AT Code of Practice (ATCOP), double decker bus, public transport, verandas, lateral and vertical clearance

Introduction 10.0%, 6.5% and 7.0% respectively.

Auckland Transport (AT) is improving the bus Due to network constraints, single decker bus network throughout the Auckland region. Part services frequencies could no longer be of this effort is to increase capacity on bus increased without major reconfiguration of the routes operating at or near full capacity road corridors. The introduction of double including the route, Central decker buses, therefore, was the preferred Business District (CBD), and the Britomart strategy for increasing capacity on high Transport Centre. Before 2012, buses on demand routes and to accommodate the these routes were already running up to 95% increasing PT patronage over the next ten of their seated capacity during peak hours. years.

The demand for public transport (PT) in Single decker buses permitted to operate in Auckland has been increasing and is projected the Auckland road network have a maximum to increase further, as reported in the dimension of 13.5m long, 2.5m wide Auckland Regional Land Transport Plan (excluding wing mirrors), and 3.1m high. (ARLTP), July 2015. Between 1994 and 2014, Proposed double decker buses have the same PT patronage more than doubled from 33 length and width but with a height of 4.25m. million trips to 72 million trips and is projected to double again in 2022. The ARLTP also AT assessed the impact of double decker bus reported that the bus services in the central operation on Auckland road network in 2012 bus corridors, Northern Express, and Botany by running a mock double decker bus on four to CBD routes experienced growth rates of key bus routes – the Northern Busway, Mount

Eden, Sandringham, and Remuera. After this trial and minor tree pruning along Fanshawe Street, double decker buses were operated on the Northern Busway. The trial also established that the larger framed buses would introduce new areas of risk to the road network and identified obstacles that require modification or removal.

Figure 2. Double decker bush crashed into a tree in South London injuring 32 people. Source:http://www.mirror.co.uk/news/uk- news/kennington-bus-crash-recap-after- 2945979

Figure 1. Double-decker bus wedged under canopy at Ipswich Hospital. Source: http://www.ipswichstar.co.uk/news/ipswich_do uble_decker_bus_wedged_under_canopy_at_i pswich_hospital_1_1382938

The initial trial was followed by a wider Figure 3. Double decker bus roof ripped off in assessment of 10 key routes shown in railway bridge accident. Source: Appendix 1 or about 200 kilometres of bus http://travel.aol.co.uk/2013/01/29/double- corridors. To ensure that the PT routes are decker-bus-roof-ripped-off-railway-bridge- safe for double decker buses and to justify the crash-hampshire/ cost of implementation within the next 10 years, AT explored different options and levels Corridor Clearance Assessment of mitigation. The cost of mitigation works was estimated at $24 million. An independent With no clear guidelines on the safe corridor economic evaluation by John Bolland envelope, AT reviewed double decker bus Consulting Ltd established that running double practices in the United Kingdom, focussing on decker buses on key routes would have safety issues. Accidents involving double significant economic benefits derived mainly decker buses show examples of hazards and from operational cost savings and traffic potential safety issues along the bus corridors benefits, outweighing the cost of mitigation in Auckland. In Figure 1, for example, a double works. decker bus crashed into the canopy of Ipswich Hospital injuring two passengers, an event

highly likely to happen in the Auckland bus routes where verandas are more common. The maximum tail swing of the bus over the Similarly, the incident shown in Figure 2 is also kerb was 0.82m for the 12.6m fixed axle bus plausible due to the prevalence of roadside and 1.14m for the 13.5m rear steer bus. trees in Auckland. Consequences of bus drivers deviating from their designated routes Front swings were measured for buses are illustrated in Figure 3, an accident that can entering a bus stop or avoiding a hazard in a easily happen in Auckland due to driver’s general lane. When entering a bus stop, the error. Incidentally, to prove this point, a double maximum front swing of the bus overhanging decker bus crashed to a verandah on the kerb was recorded as 0.63m. When Symonds St early this year when the driver avoiding a hazard at a faster speed of about unloaded passengers on a taxi stand instead 30km/hr, the maximum front swing was of a designated bus stop. recorded as 0.46m.

To further understand the hazards of operating Based on these trials, it was recommended double decker buses locally, accidents that clearances from kerb face of 0.8m on bus involving single decker buses in the Auckland stops and 0.5m on all other roads be adopted. region were analysed. From 2003 to 2012, The recommendations, however, did not take 2,431 reported incidents included 44 cases into consideration the potential impact of where buses left the carriageway or hit fixed extreme road camber and vehicle dynamic kerb-side objects. Forty-two of these incidents effects, such as body roll due to severe bus occurred on the routes being investigated for manoeuvres. AT commissioned TERNZ double decker bus use, and on 4 occasions, a Transport Research, an independent research bus mounted the kerb and struck a building. consultant specialising in transport related issues, to investigate further. As a result, As a bus turns, both of its ends rotate with the clearance of 1.0m from the kerb face on bus nearest axle acting as a pivot point. These are stops was recommended. commonly known as the front swing and the tail swing. The impact of a tail swing is typically To validate the recommendations and findings lower as buses pulling out from a bus stop is thus far, a 50m trial section of road with a 5% just starting to accelerate away from the kerb. cross-fall, the maximum allowed for sealed On the contrary, the front swing represents a roads in Auckland, was built to simulate a greater risk as a bus entering a bus stop is double decker bus approaching and leaving a decelerating from a higher speed toward the bus stop. The front and rear over swings of the kerb. bus were measured for different severe steering manoeuvres and the bus movements Prevailing Codes of Practices before ATCOP were tracked while it was in motion. A set of specified a lateral clearance of 0.5m over the robotic instruments capable of measuring footpath or road shoulder to allow buses to target prisms mounted on the left side of the manoeuvre safely close to the kerb. However, double decker bus was used, achieving an none were found specifically for double decker accuracy of within 10mm. buses and the required lateral clearance for bus stops. Hence, AT carried out trials using a These additional investigations resulted in the 12.6m fixed axle bus and a 13.5m rear steer revision of the lateral clearance on bus stops bus, which generates a larger tail swing than a from 0.8m to 1.0m measured from the kerb fixed axle bus. face. The 0.5m lateral clearance on all other roads remained. The tail swing of a bus turning out into the road from behind another parked bus was Height clearance was set at 4.6m to be investigated. Two options were tested: (i) with consistent with NZTA’s Road and Traffic the bus aligned a distance away from the kerb Guidelines RTS16: Guide to Heavy Vehicle in the manner recommended by driver trainers Management. Subsequently, however, height and (ii) with the bus wheels hard against the clearance for trees was increased to a kerb, considered poor practice but which minimum of 4.75m to allow for growth between occasionally occurs. pruning.

Figure 4 below shows the lateral and height clearances adopted to provide a safe envelope along the double decker bus corridors.

Figure 4. Lateral and height clearances for double decker bus safe corridors Figure 5. Measuring device for bus route surveys developed by Arborlab Consultancy In addition to the lateral and height clearance Services. requirements, AT determined that double greater detail in this paper as they are easily decker buses to be permitted in Auckland resolved through relocation. should have a maximum length of 12.6m and must be on fixed rear axles only. These To quantify the scope of the obstacles and restrictions were imposed to ensure that understand the level of mitigations required, maximum tail swings do not exceed the lateral entire routes were surveyed with a measuring clearance specified. device shown in Figure 5. This enables fast and cost effective data capture. A mobile data Route Survey and Results collection system was also used to store measurements, species (for trees), and A number of overhead obstructions in bus photographs for individual obstruction cross corridors were above the standard bus height referenced with its location. All survey data of 3m but lower than the double decker bus were accessible through a web based portal. height of 4.25m. The most common of these obstructions are overhanging tree branches Once these data were analysed and mapped, and low hanging power or phone lines. A route drive-and-walk-over was done to identify couple of low bridges were found – a rail hotspots that require more detailed surveys bridge on the Remuera route lower than 4.25m and investigations. Where required, structural and a pedestrian bridge on Lower Albert St in assessments of verandas were carried out. the CBD at 4.25m. Obstruction Caused by Trees Similarly, a significant number of obstacles including tree trunks and branches, shop Trees pose a significant issue for the double verandas, service poles, street signage, and decker bus network implementation due to the furniture failed to meet the recommended high amenity, environmental, heritage, and horizontal clearance from the kerb face. Street cultural value placed on them by a number of signs and furniture are not discussed in stakeholders. There are also challenges due

to the prevalence of scheduled or protected trees and trees that have not been maintained or pruned over time.

In most cases, the pruning works required could be undertaken as a permitted activity and needed only the asset or land owner approval for the works to proceed. Work on protected or scheduled trees, however, required resource consent which took up to 3 months or longer to acquire.

Case Study: Botany Route Tree Works

Along the Botany route, 1,010 trees were found encroaching the safe envelope including several heritage trees on Symonds Street – one is shown in Figure 6. Initially, 337 trees were earmarked for either heavy pruning (resulting in removal of more than 25% of the tree canopy) or complete removal.

After the major tree conflicts were identified, AT worked closely with ’s arborists to look for options that avoided heavy pruning or tree removal. Other mitigation Figure 6. Heritage tree with major limb encroaching options were considered including road lane the safe envelope in Symonds St. width adjustment, installation of parking or cycle lanes, line markings, and bus stop required removal. relocation. Particularly in Symonds Street, options such as lowering of the road level, Verandas diversion of bus services, and lifting or rotating the identified trees were also considered but Shop verandas are a common feature in discounted. Tree removal was recommended shopping districts in , particularly only as a last resort. in Auckland where a verandah is required at certain locations by legacy bylaws. This is Local community boards and other directly reflected in the number of verandas found affected stakeholders, tree owners, heritage encroaching the safe envelope on Botany, arborists, and iwi were engaged early. Where Mount Eden, Sandringham, New North Road, required, land owner approval for trees on and Dominion bus routes, where 137 private land or reserves were obtained prior to verandas had to be investigated for cutting the lodgement of resource consent back or removal. applications. As illustrated in Figure 7, most of these On the Botany route, by employing a mixture verandas were built 3m above the pavement of different engineering solutions mentioned or about the same height of a standard single above, the number of trees eventually pruned decker bus. A number of these verandas were heavily and removed was reduced to 35 and also found to be very close to the kerb or 26, respectively, and were compensated by encroaching the road because they were not replanting at least one tree for each tree compliant originally, or if they were, became removed at locations agreed with Auckland an encroachment due to subsequent road Council’s arborist. On Symonds Street, road widening. It is not surprising, therefore, that lanes were narrowed to the minimum road some verandas had already been causing width and kerbs were relocated to ensure issues to single decker buses and would be none of the heritage trees lost a major limb or more problematic for double decker buses.

Although verandas over public footpaths are privately owned and maintained, AT has the right to modify or remove them. Any modification works, however, require written approval from the property owner for building consents of relevant work to be granted.

There were also other complications in AT carrying out verandah modification works on behalf of the property owners. Normally, verandas were assessed by opening small parts of the soffit to allow a structural engineer to inspect key elements of the structure. However, based on the works completed along Khyber Pass Road, where three verandas were cut back and another one completely removed, a full understanding of the extent and of the works was possible only after all structural elements of the existing verandas were fully exposed to assess its condition.

Structural assessments also revealed that some buildings were not strong enough to support a verandah. In such cases, the option to remove the verandah and replace it with a free standing, cantilevered canopy was investigated but discounted due to ownership, Figure 7. Mock up double decker bus adjacent to maintenance, and liability issues. Works on a verandah in Mt Eden Road heritage buildings presented additional complexities as AT would be required to bring shop owners and the general public. Bus route the building or part of it to a structurally sound diversion, bus stop removal or relocation, and state should AT decide to modify or remove road width reduction were all considered. the verandah. Eventually, kerbs were relocated which left all the verandas untouched except for two Due to the constraints and difficulties outlined verandas in poor condition that had to be above, verandah modification or removal was removed by their owners. Besides completing viewed only as a last resort and other options the works within two months at a much lower were investigated and implemented, where cost of $620K, the solution also provided a viable. wider footpath for the town centre.

Case Study: Mt Eden Village Verandas Utility Services

Mt Eden Village, a town centre in central Obstructions on bus routes include low Auckland, has plenty of retail shops and hanging power or phone cables and service restaurants. Preliminary investigations poles for power and lighting. A number of revealed that 13 verandas would have to be cables were found not complying with height modified at an estimated cost of $1.5 million clearances specified for double decker bus and take at least six months to complete. routes although NZ Electricity Safety Regulations (2010) require utility service AT consulted and worked closely with the providers to maintain these cables to a affected property owners, business minimum of 5.5m above the road surface. association, and the local community board to Similarly, utility service poles were also found look for options that minimised disruption to not complying with the required lateral

clearances and had to be relocated. and time requirements. The project team worked collaboratively with several Following initial discussions with AT, utility departments within AT to ensure that legal, service providers had initiated a programme to operational, and safety requirements were not lift low hanging lines on the double decker bus compromised. In the end, a combination of routes at their cost. However, relocation costs bus stops relocations (away from power poles or in between two power poles to allow full manoeuvrability of buses in and out of bus stops), kerb build outs, parking and road marking changes, and localised power pole relocations were implemented. This approach allowed the enabling of Mt Eden route for double decker buses on time at a much lower cost.

Conclusion

Introducing double decker buses in Auckland had its challenges due to the constraints in the road network and the complexities of balancing the competing requirements of different stakeholders.

Through careful planning, consideration of all feasible options to retrofit the road corridor, and early consultation with affected stakeholders, the primary objective of providing a safe corridor along the double decker bus routes has been achieved. To date, the Botany, Northern Express 2, Mount Figure 8. Power poles near kerbs in the vicinity of Eden and Onewa Road have been enabled for a bus stop on Mount Eden Road double decker bus, a total of 70 kms of road corridor or 35% of the total for 10 routes. of poles not complying with the lateral clearances had to be borne by AT except About the authors where service poles were found to be leaning into the carriageway. Fiona Tang completed her Bachelor of

Engineering and Master of Engineering Case Study: Utility Services on Mt Eden Studies in Transportation from The University Road of Auckland and is now a Senior Engineer at

Auckland Transport’s Major Capital Group – A total of 50 power poles (see Figure 8 for South East. She led the delivery of the double example) required relocation on Mt Eden decker bus mitigation programme until Road between Balmoral Road and Mt Albert October 2016. Currently, Fiona is managing Road at an estimated cost of $2 million or the delivery of Chapel Road Realignment in $40,000 per pole mainly due to the prevalence Flat Bush and the enabling of Dominion route of rock in the area. Restricted work hours for double decker buses. along this busy road corridor and lack of readily available resources from service Remi Cruz, MIPENZ CPEng IntPE(NZ), is providers would also delay the completion of currently the Investigation and Design the work. Manager at Auckland Transport’s Major

Capital Group – South East. He led the team Other options were considered. For example, that conducted the initial assessment of the 10 undergrounding of the power cables was key routes proposed for double decker buses. explored but discarded due to higher costs

References

Auckland Transport, (2015). Auckland Regional Land Transport Plan. Auckland, p.62.

TERNZ Transport Research, (2014). Report on Kerbside Clearance Required for Double Decker Buses.

John Bolland Consulting Ltd, (2013). Business Case for Double Decker Operation on Auckland Bus Corridors. Final Report.

Auckland Council, (2015). Legacy Bylaw Provisions on Construction in the Road Corridor and Other Public Places.

New Zealand Government, (2010). Electricity (Safety) Regulations 2010. Wellington.

Ministry of Consumer Affiars, (2001). New Zealand Electrical Code of Practice for Electrical Safe Distances. Wellington.

Appendix 1 – Map of 10 key bus routes assessed for double decker buses