Sources of Guidance for Highway Design Engineers other than DMRB

There are so many sources other than DMRB applicable in the highway design, which most of the highway design engineers are not well familiar with. In the following, I have tried to explain these sources briefly.

British Standards (BS) are nationally published and peer-reviewed. The guidance on standards to be adopted for specific areas of work. Many areas of the Specification in the MCHW refer to BS’s for specific guidance on things such as stone grading curves, bitumen binder specifications, steel qualities etc.

Acts of Parliament sometimes give very specific requirements. The most common ones for our purposes are the Highways Act and the various planning acts. Various other Acts and regulations must also be observed – e.g. The Health and Safety at Work Act, COSHH (Control of Substances Hazardous to Health) and the CDM regulations as well as more general legislation such as the Disability Access Act.

Statutory Instruments (SI) – Legislation, other than Acts of Parliament, that is established by Parliament – e.g. The Traffic Signs Regulations and General Directions (TSRGD) that guides the selection of signs for specific locations. These documents can have surprisingly extensive ramifications – for instance the TSRGD is the only place where the requirements for speed control features in a 20mph zone is stated – as a condition for the use of the “entry to a 20mph zone” sign. Specific regulations cover all the various types of pedestrian crossing that are used in the UK (in every detail from the visibility needed to the types of electrical connectors to be used) and should be referred to if the need to design a crossing arises.

Road Notes – a few specialist areas are still covered by Road Notes, prepared by TRL (Transport Research Laboratory), which in general represent a former system of disseminating design information. The one that you are most likely to encounter is Road Note 39, on Surface Dressing.

Local Transport Notes – are particularly important in respect of the design guidance for Traffic Calming Works and crossings for non-motorised users – NMU’s (pedestrians, cyclists and horse-riders)

Traffic Advisory Leaflets – cover specific areas of guidance on such things as the details of specific types of NMU crossing or the use of tactile paving.

Design Bulletins – are an attempt to introduce design concepts in a more user-friendly, non-technical manner. They have been used particularly to influence the design of residential areas, where, it is argued, pedestrians are more important than cars. However, there are significant issues – notably Emergency Vehicle access, Refuse Collection Vehicle access, and statutory Utilities that make it difficult to create the rather intimate layouts that are sometimes proposed.

Roads Circulars are a level of guidance below that of a SI, which are distributed to local authorities and “other interested bodies” to introduce specific changes to government thinking in relation to specific issues.

Specific Manuals – A few areas of our work are covered by free-standing guidance e.g. The Traffic Signs Manual that adds substantial detail to TSRGD. Many aspects of the design of street lighting or traffic signals need reference to the regulations covering mains electricity installations, and it is generally best to refer such things to a specialist in that field.

CHE Memoranda (Chief Highway Engineer’s Memoranda) are typically used by the HA to announce either changes in sections of the above listed guidance or to introduce procedural changes in processing schemes. As such, they rarely introduce fundamental design data, but often give guidance as to what design choices should be made.

There are many sources of national guidance of which we all need to be aware, and it is easy to see how difficult it is to ensure total consistency across the entire range (in other words, you can often find contradictory guidance). As a result, there are cases where professional judgement is called for to decide which set of guidance is the most relevant to what we are designing.

An additional complication for anyone involved in highways infrastructure development for either housing or commercial development is that local highways authorities often have their own guidance as to how they like things to be done, and each authority tends to be different from the others. All you can do is to acquire a copy of the guidance for the area in which your project lies and work with it.