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MOTOR WAY HAVING
CENTRAL EMERGENCY LANES AND INSTALLATIONS
The following project refers to a new arrangement of the lanes for slow and fast traffic and emergency, in a bi-directional motor way, which is characterised by the fact that:
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the emergency lanes are placed on the right side of the fast and slow traffic lanes as in the ordinary motor ways;
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the emergency lanes are adjacent to each other and run at the centre of the way.
The arrangement shows some interesting improvements like:
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maximum distance between fast vehicles;
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access from both sides to the point where an emergency or an accident has occurred;
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central position of SOS line, service, counter, rest area, etc., with full and two-way utilization;
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more fluid exits and accesses to the lanes.
All this is possible on condition we think the main nodal points:
Terminal interchange
Intermediate Junction
3 Branches Spur Road
3 Branches Spur Road (Isometric)
4 Branches Spur Road
Outside Service Station and Parking Area
Inside Service Station and Parking Area
COMPARISON BETWEEN THE CURRENT PRACTISE AND THE PROJECT
This project deals with the position of the emergency lanes in a motor way where traffic is running in opposite directions on different lanes separated by a barrier.
In the present practise (diagram on the left or animation 186 KB) emergency lanes are on the right, just at the border of the track, while faster vehicles run on lanes closer to the axis of the motor way, where a continuous barrier, made of concrete, steel rails or bushes, divides the opposite bound traffic.
The relative speed between vehicles running in opposite directions is therefore maximum at the centre of the track where the distance between them is minimum.
Therefore, if an accident occurs the vehicles may roll over the barrier and crash against the incoming vehicles of the opposite lane. Even in case of a simple impact against the central barrier (on the left), the danger for the impacting vehicle to be rammed by the overtaking vehicles is greater than if the impact had been into a side barrier (on the right).
Other drawbacks of the present arrangement are that the place of an accident may only be reached through the emergency lane situated on the right of the traffic flow or by blocking the traffic coming in the opposite directionin.
Moreover no U-turns are possible for ambulances or other service vehicles or even for the users of the motor way, in case of severe traffic jams.
The goal of the proposed project (diagram on the right or animation 196 KB) is to improve safety and make the access to the place where an accident has occured easier. This is possible through a different arrangement of the emergency lanes which are now situated next to the axis of the pathway, even if they are located on the right side of the way. With this new project the traffic island, limited by the emergency lanes, may host not only a segregation barrier with controlled gaps for U-turn of vehicles in case of emergencies but also service areas or other fixed installations.
The adjacent diagrams show the arrangement of the lanes according to the present practise (on the left), and the project (on the right).
A closer look to the proposed project may be taken by analysing a number of specific solutions like:
Terminal interchange
Intermediate Junction
3 Branches Spur Road
3 Branches Spur Road (Isometric)
4 Branches Spur Road
Service Station and Parking Area
EMERGENCY LANES
The emergency lanes adjacent to the traffic island permit easy and double directional intervention of police, break-down vans, ambulances, fire brigades, etc. This is possible even if there were traffic jam.
The inherent proximity of the emergency lanes makes it possible to replace many parts of the traffic island with electronic gates like "Telepass". In addition, in case of toll-free highways, suitable U-turns gaps could allow even the reversal of the traffic and a rapid clearing of jam.
Last but not least: the single fixed axial line of installation (S.O.S. call, fire-plug, and so on) will be active even during enlargement of the motorway.
RUNNING AND OVERTAKING LANES
Moving the fast lanes from the centre to the border of the pathway means:
less risk of disastrous jump of traffic barrier and crash into the opposite carriageway;
possible elimination of modular barriers ("New Jersey barrier"), wich even preventing the above mentioned jump, may become deadly walls if the impact occurs with angles higher than 15°.
Moreover these barriers reduce the width of the overtaking lanes in the existent motor way (both in the perceptive sense and, sometimes, in the reality) and, under special light conditions, they look scarcely different from the road layer.
SERVICE STATION AND PARKING AREAS
In some cases most of the traffic flows in one direction only. A central service station accessible from both traffic directions could provide better service under the same number of pumps and attendants.
The solution with two lateral areas and carriageways inside a channel looks preferable: this will provide acoustic comfort for resting people and avoid the too big embrace with smooth cambers of two bypassing ways.
This kind of petrol service and rest areas means accommodate room enough for U-turns, and minimal meeting and interchange opportunities.
JUNCTIONS AND EXITS
Please see the following:
Terminal interchange
Intermediate Junction
3 Branches Spur Road
3 Branches Spur Road (Isometric)
4 Branches Spur Road
Service Station and Parking Area
TERMINAL INTERCHANGE
Before the toll gate or open entrance an overpass is necessary for transposing the carriageway.
Intermediate Junction
3 Branches Spur Road
3 Branches Isometric Spur Road
4 Branches Spur Road
Service Station and Parking area
Intermediate Junction
This road spur is similar to the current which joins the normal road system. Still it is more fluent and little more expensive, because of the 3 levels underpassing.
Terminal interchange
3 Branches Spur Road
3 Branches Spur Road (Isometric)
4 Branches Spur Road
Service Station and Parking area
THREE BRANCHES SPUR ROAD
The function of this is similar to the following Isometric spur road, but one directrix is privileged.
Terminal interchange
Intermediate Junction
3 Branches Isometric Spur Road
4 Branches Spur Road
Service Station and Parking area
3 BRANCHES ISOMETRIC SPUR ROAD
Spur Road for three directions of same importance. This is a very compact and fluent joint (without "halter" like the current trumpet-spur), but it involves some additional costs.
Terminal interchange
Intermediate Junction
3 Branches spur road
4 Branches Spur Road
Service Station and Parking Area
FOUR BRANCHES SPUR ROAD
With two "halters" and six direct joints,this is a very expensive spur. But it 'looks' very safe and fluent because it needs no obstructing between the in and out coming vehicles. This last feature cannot be reached with usual four-leaved joint.
Terminal interchange
Intermediate Junction
3 Branches spur road
3 Branches Isometric Spur Road
Service Station and Parking Area
SERVICE STATION AND PARKING AREA
The highway runs inside a channel or underground, this provides better acoustic isolation and comfort for resting people. The two overpassing bridges allow U-turns and meeting or exchange opportunities.
Terminal interchange
3 Branches spur road
3 Branches Isometric Spur Road
4 Branches Spur Road
CONCLUSION
As a result of the analysis the following features may be pointed out:
- The incoming spurs are always preceded by the outgoing spurs (the same doesn't happen in usual spur roads where a mutual dangerous obstructing happens most often).
- The incoming-acceleration ramps are normally overpassing, while the outgoing-deceleration ramps are
underpassing, in facts it is almost impossible that an accelerating vehicle may crash into and roll over a side barrier, on the contrary this may happen to a decelerating vehicle.
- The "telepass" gates are in the opposite side. This position saves the inverse utilization of central gates, like in the present practise. The project cancel the dangerous position near the emergency lanes, because remain the same direction of the overtaking lanes.
- Except for a few cases the junctions are direct and intuitive, without knots.
- The depicted junctions are very compact, with some 3 level layering, while the overpassings (or underpassings) take only place between single carriageways.
Top
Comparison
Terminal interchange
Intermediate Junction
3 Branches spur road
3 Branches Isometric Spur Road
4 Branches Spur Road
Service Station and Parking area
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Thanks for your attention.
Arch. VincEnzo Ricceri - Milan - Italy (Copyright
1992)
See the contribution to the S.I.I.V 2000  convention
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