Appendix 1a
HIGHWAY STRUCTURES COMMUTED SUMS REPORT
1.0
Background
1.1
A commuted sum is a calculated sum of money necessary to compensate for the
transfer of a liability from one organisation to another.
1.2
The commuted sum for a highway structure should cover the future costs of regular
inspections, maintenance, repair and eventual reconstruction.
1.3
There are two primary situations in which a local authority may wish to charge a
commuted sum:

adoption of a highway structure (bridge, retaining wall or culvert) under Section 38 or
278 of the Highways Act 1980;

transfer of a highway structure from another public body or from private ownership to
the highway authority
2.0
Current Situation
2.1
Trafford Council only charges a commuted sum on an ad hoc basis for the adoption
of highway structures (adopting some structures but not others depending on
individual circumstances).
2.2
Leaving highway structures unadopted can lead to problems for highway users in the
future. This has been recognised by some highway authorities, which adopt all new
highway structures proposed under section 38 and 278 agreements.
2.3
The Department for Transport recommends that commuted sums should be charged
for highway structures such as Bridges, retaining walls and culverts.
3.0
Calculation of Commuted Sum
3.1
Network Rail has developed a nationally recognised method for calculating
commuted sums.
3.2
An example showing how a commuted sum is calculated using this method is shown
in Appendix A. On average the commuted sum is usually between 1020% of the
construction cost.
4.0
Option 1: Status Quo
This allows the Council discretion when deciding which highway structures should be
adopted. This is currently the case and decisions are based on individuals’
appraisals. It can however be very difficult to agree the cost of commuted sum when
the commuted sum hasn’t been clearly identified in the Council’s Charges Report.
Unadopted structures are a potential problem from a health and safety point of view
in the future if the developer fails to maintain.
Appendix 1a
5.0
Option 2: Introduce Charges For All Highway Structures
5.1
The current revenue budget for bridges is only £55k/annum. If a return of between
10-20% of the cost of new highway structures constructed as part of section 38 or
278 agreements could be secured, the additional income would significantly support
the maintenance of the Council’s existing highway structures maintenance budget.
6.0
Recommendation
6.1
The permutations for income generation are endless (not least the number and size
of new section 38 and 278 highway structures per year). Any adjustments to
budgets would have to be based on a trial basis.
6.2
A clear charging policy would remove the need for individual appraisal to be carried
out and provide a clear charging mechanism for developers to follow.
6.3
Invariably there is also a risk that developers responsible for privately owned
highway structures will disappear over the years leaving the Council in dispute with
its own Council Tax payers.
6.3
The recommendation therefore is that option 2 should be approved.
Appendix 1b
APPENDIX 1b – CALCULATION OF COMMUTED SUMS
1.
Method
The following method, which is a nationally recognised method originally developed
by Network Rail shall be used to calculate commuted sums to cover the future costs
of regular inspection, maintenance, repair and eventual reconstruction of a highway
structure.
a)
Estimate/obtain the cost of constructing the highway structure and for bridges
split this up into cost of substructure and superstructure. The costs of piling
(excluding that portion of any pile that remain above foundation level as part
of the substructure), earthworks (excluding any reinforced fill), services and
the proportion of contract preliminaries applicable to these items shall not be
included. The cost shall be increased by 12% to allow for the design and
supervision of maintenance and renewal works and by another 7% for railway
bridges to allow for Network Rail charges.
b)
Calculate the annual cost of maintaining and renewing the highway structure
by applying the following percentages as may be appropriate to the
estimated/actual cost of each part of the highway structure obtained in (a)
above. These percentages are to be taken as applying to the various types of
sub or superstructure as a whole, e.g. the percentage appropriate to an
encased steel superstructure of Type 2(1) (i.e. 1%) would be applied to the
whole superstructure and not confined to the steel portion of it.
Substructure of Bridges, Box Type Structures and Retaining Walls
Mass concrete, brick or masonry
(not applicable to mass concrete abutments relying for stability
on strutting support of superstructure in which case use
0.375%
Reinforced concrete/brickwork
0.75%
Cast Iron
0.375%
Encased steelwork and wrought iron
0.625%
Exposed steelwork and wrought iron
1.5%
Reinforced Earth
0.75%
Reinforced concrete box type structures
0.8%
0.75%
Appendix 1b
Superstructure of Bridges
Encased steel and wrought iron:(1)
Wholly encased
(2)
Partially encased:i)
ii)
0.625%
underside only of girders exposed, e.g.
longitudinal girders with jack arches
springing from bottom flanges
1%
All other types
1.5%
Cast iron
0.375%
Exposed steelwork and wrought iron
1.5%
Brick or masonry
0.5%
Mass concrete
0.375%
Reinforced concrete arches
0.75%
Reinforced and prestressed concrete decks:i)
Precast units
0.75%
ii)
Cast in-situ
1%
Timber
(c)
Calculate the commuted sum by multiplying
the annual cost of maintaining and renewing the
structure calculated in (b) above by 28.5. The factor
of 28.5 is based on the real rate of return on long
term investments (i.e. after taking account of
inflation) of 3½ %. The factor is obtained by
dividing 100 by 3½%.
2%