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The Project Control Framework
This framework sets out how we, together with the Department for Transport, manage and deliver major road improvement projects.
The Tunnel
A3 Hindhead Improvement
The Tunnel
The tunnel is 1.2 miles (1.83km) long comprising about 1 mile (1.77km) of bored tunnel and approximately 98 ft (30 metres) of cut and cover at either end. The maximum depth of tunnel below ground is about 200 ft (65m )at Gibbet Hill, (measured to the top of the tunnel).
The tunnel will have two separate bores. Each bore will include a 23 ft (7.3m) wide 2 lane carriageway with 3.9 ft (1.2m) wide verges on each side. The verges are wide enough for emergency use by a disabled person in a wheel chair. Each bore will have a maintained headroom of 17 ft (5.03m), together with a further clearance of 9.8 inches (250mm) to the underside of any plant suspended above the vehicle gauge as a safeguard against flapping tarpaulins and ropes.
The tunnel bores will be approximately parallel and linked by pedestrian cross-passages at approximately every 328 ft (100m) throughout the tunnel. The tunnelling method proposed by Balfour Beatty is the Sprayed Concrete Lining method (SCL).
The tunnel alignment is in the middle of the Upper Hythe beds at the southern portal. These beds consist of silt sand with rock bands. Further north, it passes through the Upper Hythe beds where the percentage of rock starts to increase and then in the Lower Hythe beds there is rock with minor sand bands.
A larger image of the cross section is available to view here.
Questions and Answers on the operation of the tunnel and new access arrangements
Q. What is the speed limit for the tunnel?
A. The speed limit is 70 mph and there are national speed limit signs in the tunnel reminding you of this. If there is an incident in the tunnel such as a breakdown then these signs will change to display a 40 mph speed limit.
Q. Are there speed cameras in the tunnel?
A. No. The system measures your average speed between two fixed points outside the tunnel where the yellow cameras can be seen.
Q. What is the category for dangerous goods?
A. The classification code is A, there are no restrictions for carrying dangerous goods through the tunnel.
Q. How are the cats eyes displayed through the tunnel?
A. During normal operation of the tunnel, alternate LED cats eyes will be displayed.
If two way working is introduced, all the LED cats eyes will be displayed forming a solid line.
Q. Are you allowed to over take in the tunnel?
A. It is legally allowed to overtake in the tunnel, if the driver deems it safe to do so and conditions permit. The line markings comprising a 4m line and 0.5m gap are similar to those used at right turn ghost island. And a similar principle applies you may cross them if it is safe to do so. If a tunnel is in two way operation then the lane control signs ban you from using the right hand carriageway and that message is enforced by all the catseyes being illuminated as opposed to every other one in normal operation.
Q. Do you need to use dipped head lights while travelling through the tunnel?
A. The lighting has been designed so that you do not need to use dipped headlights. However you may find it helpful to turn on your side lights to light up your instrument panel
Q. How do I access the Youth Hostel
A. Leave the A3 at the Thursley Junction, If you are coming from the north then after leaving the A3 turn right at the top of the slip road then take a left after the bridge and then left again onto the Old Portsmouth Road then take the next right into Boundless Road following the sign to Boundless and YHA. If you are coming from the south then take the first left after leaving the A3 again following the sign to Boundless and YHA. At the Boundless Road/Punchbowl Lane junction follow the signs to the YHA along Punchbowl Lane.
Q. How do I access the A3 from the A287?
A. Travel to the Hindhead Crossroads as before and then either turn left from the Haslemere Road or right from the Tilford Road along the old A3, now renamed A333, to the Hazel Grove junction.
Q. I am disabled, are there any special procedures I should aware of if I am required to evacuate the tunnel for an emergency?
A. There are no special procedures since much depends on your disability. The verges of the tunnel are designed to be wide enough for wheelchair access and the kerbs are lowered at each emergency point and cross passage. If you are able to do so then in an emergency you should communicate with the tunnel control room via an emergency phone. If not then be assured you will be under surveillance and if necessary the control room will dispatch a supervisor to assist you. The telephones are equipped with a text service for those hard of hearing.
General Questions about the Scheme
Q. Will there be a services tunnel between the two main bores?
A. No, we do not need to provide a separate tunnel to accommodate services.
Q. What happens if the electricity supply fails?
A. The tunnel will receive its power supplies from two power networks, one towards the north and one towards the south. So if one supply fails the other one will take over. There will be back-up power supplies, which will come into use should both supplies fail or should the supply within the tunnel fail for some reason.
Q. What happens if the ventilation fans break down?
A. Under normal weather and operating conditions, the movement of traffic itself would be sufficient to create the draft through each tunnel necessary to ventilate exhaust fumes. The ventilation system is designed to operate only when weather conditions (such as high winds) or traffic congestion means that exhaust fumes start to build up. Additionally the ventilation system is designed to operate successfully even if some of the fans break down.
Q. Will any road users be banned from the tunnel?
A. Yes, in the interest of safety, cyclists, pedestrians, equestrians and motorcycles below 50cc will be banned from the tunnel. Cyclists, pedestrians and equestrians will be provided with an alternative route across Hindhead Common and motocycles below 50cc will be diverted via Thursley and the Tilford Road.
Q. Where have similar road tunnels been built in the UK?
A. Similar tunnels constructed in the UK in recent years are at Roundhill on the A20 and at Southwick on the A27.
Q. How much earth will be excavated from the tunnels and what will you do with it?
A. There will be around 300,000 cubic metres of spoil generated which will all be used to build the highway embankments and earthbunds on the northern side of the tunnel. No spoil will be taken away from the site.
Q. Will there be any settlement above the tunnel?
A. Our calculations predict that any settlement is unlikely to be noticeable; however we will monitor this during all tunnelling operations
Q. What safety features are you incorporating into the design?
A. The tunnel will have:
- high quality lighting and ventilation
- continuous traffic monitoring and CCTV surveillance
- early automatic detection of vehicle breakdowns, accidents and fires
- quick appropriate information to drivers using automatic variable message signing, radio interrupt systems and loudspeakers
- well equipped emergency points with fire extinguishers, a manual call button and emergency telephones that can be used by disabled persons
- easily identifiable safe escape routes.
In addition we will develop plans to:
- ensure emergency vehicles can get to the tunnel quickly
- route traffic away from the tunnel if blocked by an incident
- assess the risks from all credible hazards
- manage incidents.
These issues will be developed in association with the Tunnel Design and Safety Consultative Group, which comprises representatives of emergency services, local authorities and the Environment Agency.
