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  1. The project will provide a new river crossing between the Brooker Highway and Midland Highway, including connections to the Lyell Highway.
  2. The new bridge will have a minimum design speed of 80km/h.
  3. The new bridge will include two lanes in each direction.
  4. The project will include the grade separation of the Lyell Highway Junction at Granton and Black Snake Lane at Granton.
  5. The new bridge will have a minimum airdraft clearance consistent with the navigable clearance under the Bowen Bridge.
  6. The new bridge will include a shared path for pedestrians and cyclists.
  7. The new bridge will include safety screens and barriers.
  8. The new bridge will not preclude the future use of the existing rail corridor.

1 Project extents

  1. The project is to provide a new river crossing between the four-lane sections to the south (Brooker Hwy) and north (Midland Hwy). The project must also include connectivity to the surrounding road network, particularly the Lyell Highway. The project extents are to be minimised as much as possible (to limit costs) while achieving these connectivity requirements.

2Design speed and posted speed

  1. The Brooker Highway south of Granton has a posted speed of 100km/h. The Midland Highway north of East Derwent Highway has a posted speed of 110km/h.
  2. Reduction of the design speed allows for a slightly tighter curve at the southern side, leading to moderate cost savings due to reduced bridge width on the curve, reduced bridge length under some design scenarios, and increased construction access from the causeway. It is therefore proposed that the minimum design speed be 80km/h.
  3. A ‘Safe Systems Assessment’ is proposed to ensure that the design speed is appropriate.

3Number of traffic lanes

  1. The current and forecast traffic volumes warrant two lanes in each direction on the Midland Highway at this point and it is recommended that this is a minimum requirement.
  2. It is recommended that the Brooker Highway (northbound) be upgraded to include two lanes right through to the bridge. The southbound carriageway would retain two lanes.
  3. Given the current configuration of the East Derwent Highway interchange, it would be possible to maintain the current width of the Midland Highway north of Boyer Road. However, this would then cause a bottleneck on the National Highway at this point. Given the cost to widen the highway to include an extra southbound lane for this short section is relatively low, it is recommended that the two lanes in each direction is maintained north of the bridge.

4Grade separation of intersections

  1. Grade separation is proposed at the following locations to ensure the efficient flow of traffic with minimal queuing or vehicle conflict points
    • Lyell Highway Junction, Granton
    • Black Snake Road, Granton

5Road height and airdraft clearance

  1. It is recommended that the design road levels must consider Q100 storm events, forecast sea level rise, storm surges and measures to protect against structural damage from overtopping.
  2. It is recommended that a minimum bridge airdraft clearance be consistent with the navigable clearance under the Bowen Bridge. The net cost impact of providing this clearance rather than eight metres has been assessed as low and this will avoid any additional restrictions on navigation of the river between the Bowen Bridge and New Norfolk.

6Provisions for pedestrians and cyclists

  1. It is recommended that a single three metre clear width shared pathway be provided. There is no warrant for a pathway on both carriageways, given the available funding and the cost of a second pathway.
  2. Making no allowance for a shared pathway would have a significant cost saving but would not provide the level of functionality that has been previously committed. Options that utilise existing structures may provide a lower-cost alternative to a shared pathway on a new bridge.
  3. The pathway must achieve design standards required for access by disabled persons (i.e must be DDA compliant).

7Provisions for throw screens and barriers

It is recommended to include barriers to thrown objects on a bridge over land to protect traffic and people underneath from objects being thrown from above.

  1. The location, height, form and cost to achieve this requirement will be investigated and agreed during the Early Contractor Involvement (ECI) phase.

8Provision for future rail

  1. It is not possible to provide for rail on the new bridge within the available funding.
  2. It is recommended that the functional user requirements include that the design must not preclude the future use of the existing rail corridor. This would ensure, for example, that there is sufficient clearance above and beside the existing rail corridor.