As you are most likely aware, Glasgow's motorways are pretty unique! There's nothing else like them in the UK - in fact you could argue the M8 has more in common with an American Highway. But it's not just the bridges and junctions that are unusual - the signing is strange too!
Back in the 1960s there were no sign manuals for urban motorways giving scheme designers the freedom to come up with whatever weird and wonderful ideas they liked. That's exactly what happened in Glasgow. The result is a form of signage that roughly follows the ideas put in place elsewhere, but with enough differences to make them stand out.
Over the past forty years the design of the Glasgow sign gantry has basically remained the same - two white legs, a white box and a front mounted sign that is illuminated from behind. Of course in reality it's slightly more complex than that and they are pretty intricate structures that make other UK sign gantries seem simplistic in comparison.
Today there are well over 130 "Glasgow Type" gantries on the network and these are located along the M8 from junctions 8 to 29, the A739 Clyde Tunnel Expressway, the A814 Clydeside Expressway, the M77 from junctions 1 to 4, the A737, the M80 from junctions 1 to 3 and on the new M74 from junctions 1 to 2A. A variant of the familiar design can be seen on the new M80 southbound from junction 5.
The first "Glasgow style" sign gantries were erected as part of the construction of the Kingston Bridge and its approach roads. The works which were completed in June 1970, saw a total of four signs installed - two northbound and two southbound.
Neither the Interim Ring Road Report (1962) nor the Highway Plan (1965) had laid out any specific designs for signage on the Glasgow motorways other than to highlight the difficulties posed by the close proximity of interchanges. A concept drawing was produced by Alexander Duncan Bell (as seen on page 86 of the Highway Plan) as part of a visualisation of the Kingston Bridge Complex. This drawing marks the earliest appearance of a Glasgow type gantry in any official documentation although it is unknown if the final design evolved from this.
Glasgow Corporation passed responsibility for the design of the Ring Road signage to Scott Wilson Kirkpatrick (SWK), who had been appointed designers of the north flank. It had been agreed with the Scottish Development Department that the larger "X-heights" of letters used on the signs of rural motorways would not be required on the Ring Road. This meant a much reduced sign face area would be required. It was at this stage that internally lit overhead sign gantries were devised by Gavin Walker of the SWK Bridges team. His proposal was accepted due to its low visual impact and reasonably low construction cost.
The design was shared with W.A Fairhurst who were designing the west flank and Kingston Bridge contracts to ensure consistancy of approach.
It was accepted at an early stage that the gantries could provide lane control in addition to advanced directional signage – particularly through the use of new technology. Details on this aspect can be found below.
Walker envisaged a Vierendeel Truss for the main frame of the gantries with the full structure comprising the following elements:
1. Near and offside support legs (basically 2 rectangular hollow sections with base plates to allow connections to the foundations)
2. A Main Frame (made up of rectangular hollow sections) - Over clad on the front and rear faces with a Rigidal cladding system. Rows of cladding angles/rails were provided for additional support. The soffit and roof were clad with steel sheets riveted directly into the main steelwork. The main frame was held in place between the supports via bolted connections - although the design of this detail varied depending on the designer. Access hatches were provided for inspection access/maintenance works. Internal timber walkways were installed on the floor of main frame.
3. A Sub Frame (made up of smaller hollow sections and welded to main frame). Its surround was clad with black steel sheeting.
4. A Sign Face - 15mm thick acrylic sheets hung from the front of the sub frame over its full height. Signage destinations/colours provided by painting ink (usually) on the internal face. No defined standards for urban signage were in place by this point however usual MoT guidelines were followed to an extent – particularly with regards to legends etc.
5. Internal Electrics - sign lighting provided through the use of several dozen fluorescent battens. Signal units mounted behind acrylic panels - a clear window was provided for the units and their flashers.
The entire structure was finished with a three coat protective paint system. The top coat used was white – again devised by Walker to reduce its visual impact. Construction of the gantries took place as part of the scheme finishing works. The main structural elements were installed on site before cladding, signing and electrics were installed. (See photo from April 1971). The gantries generally maintained minimum headroom of 5.3m. The final approved design was quite unique and unlike any urban signage developed elsewhere in the UK. By providing an internal inspection chamber and keeping electrical equipment away from the elements it was anticipated that maintenance costs would be reduced and life expectancy increased. By 1972 a further twelve gantries had been installed.
Despite their almost identical appearance there were several subtle differences adopted by the designers at each consultant. Fairhurst's Kingston gantries had wider legs (as seen on the Kingston Bridge), while SWK's generally had a narrower and shorter truss making them much smaller overall. This is particularly evident on the sign face where SWK gantries have less room for destinations, route numbers etc.
Several gantries were installed on the Ring Road prior to the completion of the adjoining section - for example Woodside Viaduct was completed before Charing Cross. This led to the situation where some gantries had blank sign faces for over a year. When the new section of road was about to open the required destinations were stencilled onto the sign face by hand. A couple of blank sign faces can be seen on the photographs opposite.
On completion of the Ring Road in 1972 it was agreed that similar sign gantries would be used on upcoming projects including the Clydeside Expressway and the Renfrew and Monkland Motorways.
Glasgow was at the forefront of motorway ITS (Intelligent Transport Systems). From the outset it was envisaged that the gantries erected on the new ring road would be more than just directional signs. New and emerging technology meant it was possible to provide live traffic control through the use of electronic signal units for the first time. These units could be positioned above each traffic lane and be controlled from a central location in conjunction with a state of the art CCTV system. Glasgow Corporation was keen to see such a system installed on all the new roads being constructed in the city though it was clear that much planning and design would be required before it could go live.
Working in conjunction with the Transport and Road Research Laboratory (TRRL) a plan outlining what infrastructure would be required was published before the opening of Kingston Bridge section of the ring road in 1970. As a result all sign gantries erected were provided with the necessary technology to allow them to be connected to a centrally controlled system at a later date. Each gantry was fitted with the required number of signal units but the infrastructure required to connect them would come later once a practical design and operational programme was developed. Despite this lack of connectivity the units were powered locally and were capable of displaying a variety of characters. For the first few years all gantries displayed a downward pointing arrow above each lane. This can be seen in some of the photos above.
To Be Continued...