Layout of Compact Grade Separated Junctions Summary:This Standard sets out the layout requirements for compact grade separated junctions. It gives recommendations for the application of compact grade separation to existing at grade junctions and to new routes incorporating junctions of this type. THE HIGHWAYS AGENCYTD 40/94 THE SCOTTISH OFFICE DEVELOPMENT DEPARTMENT THE WELSH OFFICE Y SWYDDFA GYMREIG THE DEPARTMENT OF THE ENVIRONMENT FOR NORTHERN IRELAND Volume 6 Section 2 Part 5 TD 40/94Registration of Amendments ELECTRONIC COPY - NOT FOR USE OUTSIDE THE AGENCY July 1994PAPER COPIES OF THIS ELECTRONIC DOCUMENT ARE UNCONTROLLED REGISTRATION OF AMENDMENTS AmendPage NoSignature Organisation, this would not result in significant b.provide a safer means of crossing high speedorganisations should confirm its application to routes for all road users;particular schemes with the Overseeing Organisation. c.reduce the environmental impact of grade separated junctions by providing a compact junction layout; d.regulate and maintain vehicle speed for minor route traffic through the junction at a level appropriate to the layout standards; e.extend the use of grade separation; f.remove right turn manoeuvres from high speed roads. and specifically:- g.minimise land take; h.provide an operationally efficient junction layout; i.provide an economic solution for the modification of existing junctions to grade separation standards. Scope 1.8This standard sets out the layout requirements for new compact grade separated junctions and for the upgrading of existing at grade junctions. 1.9Recommendations are given on the siting of the junctions, flow standards, layout alternatives, geometric design and safety for all classes of road users. Some aspects of signs and road markings are included for completeness, though the full policy and detailed guidance on these matters are given in the Traffic Signs Manual. 1.10This standard also gives recommendations for the identification of existing junctions to which compact grade separation may be applied. improvement of trunk roads currently being prepared additional expense or delay progress. Design Definitions 1.12The terminology follows where possible the definitions contained in BS 6100: Subsection 2.4.1:1990. and in TD 22 (DMRB 6.2.1). 1.13The following additional terms have been defined for use in this Standard. Compact Grade Separated Junction: A grade separated junction designed in accordance with this standard. Compact Connector Road: In the context of compact grade separated junctions a two way connector road between the major and minor roads. 1.14Where the term Full Grade Separation is used in this standard it refers specifically to the standards contained in TD 22 (DMRB 6.2.1). Grade Separation refers to both full and compact types of grade separation. Volume 6 Section 2Chapter 2 Part 5 TD 40/94Design Procedures ELECTRONIC COPY - NOT FOR USE OUTSIDE THE AGENCY July 1994PAPER COPIES OF THIS ELECTRONIC DOCUMENT ARE UNCONTROLLED2/1 General Principles 2.1The introduction of design standards for compact grade separation is primarily aimed at improving safety for all road users. At all stages in the design and construction of the junction it is of paramount importance that safety aspects are fully investigated and considered. 2.2This standard shall be applied in the design process to both the improvement of existing at grade junctions on single and dual carriageways, and to the design of junctions on new single and dual carriageway routes. Compact grade separation requires in all cases the provision of either a section of single lane dualling or a full dual carriageway on the major route. 2.3The standards for compact grade separation have in most instances been rigorously set in order to minimise the variation in designs to prevent confusion for the road user. Those items which do permit a degree of variation at the discretion of the designer are: a.Junction configurations; b.Horizontal radii on compact connector road (desirable minimum radius with a relaxation of one design speed step) c.Vertical Curvature; (desirable minimum radius with a relaxation of one design speed step) d.Carriageway Width; (three options and a one step relaxation) e.Curve Widening. (three options are permitted for each radius) Junction Strategy 2.4Junction design shall provide an understandable progression of standards for the driver and therefore sequences of junctions should not involve many different layout types. The introduction of a compact grade separation to replace an existing at grade junction will have an effect within the route, beyond the immediate limit of the junction. It is therefore essential to assess the effect upon the network and prepare a junction strategy. The siting of the compact grade separated junction will require careful consideration of the degree of access to be provided. 2.7Where a compact grade separated junction or junctions are being considered the following matters shall be ta