This assignment addresses the following module outcomes:
MO1 Apply design principles and standards to transport infrastructure geometric design problems
MO2 Apply design principles and standards to transport infrastructure construction problems
MO3 Generate a number of design options to solve an open ended problem
MO4 Synthesise specifications, standards and site conditions to develop final detailed solutions.
Metrobus South-west facing on and off slip-roads on the M32 at Stoke Lane, Bristol
Metrobus (for more information click here) has been constructed in Bristol. The plan of the routes shown here indicates the routes for Metrobus. Metrobuses on the proposed North Fringe to Hengrove route need to interchange between the M32 (South) and Stoke Lane (North).
Some people suggested during the planning stages that the bridge and slip road arrangement constructed for Metrobus to leave the M32 were unnecessarily costly because of the requirement for the additional bridge. This recently constructed bridge lies North of the current Stoke Lane bridge and its plans are shown in the file ‘Metrobus proposals at Stoke Lane.pdf’ on Blackboard.
Your task is to develop an alternative design which provides South Facing slip-roads just for Metrobus onto and off the M32 from Stoke Lane. This would have cost considerably less, and also would have allowed for shorter journey times between the M32 and Stoke Lane.
Assumptions for Metrobus design
The following table identifies parameters that you will need to make assumptions about in respect of the suggested alternative of South facing on- and off-ramps connecting Stoke Lane to the M32 for Metrobus. Relevant document ID and paragraphs and tables from the Design Manual for Roads and Bridges (DMRB) have been identified. They can be found in the Road Layout section of th DMRB Website.
Note that the design speed for the motorway main line is 120 km/hr, and the speed limit currently on Stoke Lane is 40 mph, hence a design speed of 70 km/hr.
Note that you should clearly state whether you have considered relaxations and whether you have then applied these to any parameters.
Finally, please make sure you are familiar with the verbal forms used in Design Manual For Roads and Bridges. See page 5 of GG101 in the General Governance and Scheme Governance section of the DMRB website.
Parameter |
Para / Table |
Connector road design Speed |
Table 5.4 |
Stopping sight distance |
CD122 Para 5.13 and CD109 Table 2.10 |
Horizontal curve radius |
Para 5.10 |
Maximum vertical grade on slip road |
CD122 Para 5.7 and CD123 para 5.3 and 5.3.1 |
Merge onto mainline: Length of entry taper / nose ratio / nose length |
Figure 3.14a and Table 3.21 |
Diverge from mainline dimensions: Length of exit lane / nose ratio / nose length |
Figure 3.30a and Table 3.31 |
Widths of verge / hard-shoulder / running lane /hard-strip / verge |
CD 122 Table 5.17b and CD127 Figure 2.1.1N1b |
Priority junction corner radii |
Para 5.6.1 |
Taper to ghost island for right turn pocket for the on-slip |
Table 6.1.1 |
Ghost island dimensions: 1) a, the turning length; 2) b the deceleration length; 3) c the through lane width; 4) d the turning lane width; and, 5) e the direct taper length. |
Fig 6.3a, Para 6.4, Para 6.8, Para 6.10.1 and Para 6.11 and Table 5.22 |