Prof. Ivan Legac, D. Sc. Faculty of Transport and Traffic Engineering, University of Zagreb,
Vukelićeva 4, 10 000 Zagreb, tel:0038512380228, e-mail:
Goran Legac, B. Eng., Croatian motorways, Širolina 4, 10 000 Zagreb, tel: 0038514694444, e-mail:
Luka Novačko, B. Eng., Gruška 18. 10 000 Zagreb, tel:00385915122286,
e-mail:
MODELLING AND ARRANGEMENT OF THE OFFICIAL PASSAGES IN THE MEDIAN STRIP OF MOTORWAYS
Abstract
Occasional tragic accidents caused by semi-circular turning of vehicles on the passages in the median strips (central reserves) of motorways have instigated research on the Croatian motorway network. The results of the theoretical and practical research with the analysis of experience in the European countries have pointed out the need for a more serious approach to this issue. Preliminary results suggest standardization of forms, equipment and distance between passages. The official passages should be completely closed and emergency vehicles or vehicles for motorway maintenance should have to use lateral passages for changing of direction on the crossovers. On the basis of geometrical measuring and practice in some European countries it is recommended to design passages in the median strip of motorways for the traffic flow speed of 60 and 80 km/h. The length of the passages for the mentioned speeds is 90 or 135 m. In the respect of operative length of motorway sections for road construction works, distances between passages should be among 3 and 5 km.
Key words: traffic safety, motorway maintenance, accident situations, official passages
regularization
INTRODUCTION
The Republic of Croatia currently has a motorway and expressway network of 1050 km. With the increase of new motorway kilometres, the problem of reduced traffic safety has been noticed, caused by prohibited semi-circular turning of vehicles on the open passages in the median strip of motorways, as well as by the passing of vehicles to the opposite roadway in accident situations, etc.
The analysis of the current situation showed that even more than 70% of passages on some Croatian motorways are opened, equipment of passages is not standardized and arrangement of passages is inadequate and unsystematic.
The above mentioned was a motive for more detailed research of the issue of modelling and arrangement of passages, emergency service organization etc. The research resulted in some conclusions and recommendations, which are not yet final and their acceptance and implementation into Croatian regulatory acts is still due.
EXISTING REGULATION AND PRACTICE
The problem of modelling and arrangement of the official passages in the median strip of motorways is not fully defined on the European Union level, and it is left for the member countries to define the mentioned field within their national acts.
Documents which partly regulate this field on the EU level are:
- EN 1317-1...6 – Road restraint systems – they are mainly dealing with criteria for safety barriers test methods (6).
- Directive 2004/54/EC on minimum safety requirements for tunnels in the Trans-European Road Network – the document prescribes that there must be a crossing over the median strip in front of the tunnels with two or more tubes (2).
SRP/TEM (Trans European North-South Motorway) – standard for motorway modelling (2002) defines passages on every 2-4 km of motorway for redirection of traffic and semi-circular turning of emergency service vehicles (3).
Table 1. List of regulations for passages in the median strip of motorways in some countries
Country (regulations /norms) / Distance between passages [km] / Passage length Lp [m] / Traffic flow speed V [km/h]
Germany (RSA,RPS) / 3 – 4 / 135 / 80
Slovenia (TSC 02.210) / ≤ 2 / 135 / 90 * / 60
Italy (Act -2001) / ≤ 2 / 80 / 34 ** / -
Slovakia (STN 736101) / 2 – 3 / 120 / 135 *** / -
TEM (SRP 2002) / 2 – 4 / - / -
Croatia (JUS S.4.110) / 3 / - / -
Interpretation:
* ( 135 m = length for redirection of two traffic lanes / 90 m = length for redirection of one traffic lane)
** ( 80 m = minimum length for redirection / 34 m = maximum length for emergency vehicles)
***( passage length in straight line / passage length in bend)
The data showing that distances between passages range between 0.26 and 19.62 km and lenghts of passages range between 36 and 165 m suggest the need for prompt regularization of this issue in the Republic of Croatia. Equipment and protection of passages are not standardized either, and a large number of temporary solutions is also alarming (for instance: plastic New Jersey).
Figure 1.:Partially opened passage in the median strip(CRO)
MODELLING OF OFFICIAL PASSAGES
Traffic-dynamic demands
Traffic-dynamic demands are based on passage speed (60-80 km/h) and configuration properties of median strips.
The calculation of passage length LP (m) is derived from trajectory elements of vehicles crossing from one direction of motorway to another (1):
Figure 2. Trajectory elements of vehicles crossing from one direction of motorway to another
The following is derived from the right-angled triangle:
R – radius of curvature R = |AC|
S – median strip width (3-4 m)
P – traffic lane width
Fulfilment of traffic-dynamic demands for traffic flow speed V = 80 km/h would be ensured with radius of curvature R ≥ 250m, and for the speed of V = 60km/h the radius would be R ≥ 120m. In respect of traffic safety, the mentioned radii are considered as minimum and greater radii and lengths will be applied in practice. In Germany, for example, construction of passage LP = 135 m is based on circular turns with the radius R = 350 m (V = 80 km/h) (13).
Geometrical measurements (in straight lines and bends)
The following settings were taken into consideration when determining the passage length:
- traffic lane width 3.75 (3.50) m
- median strip width 3.00 and 4.00 m
- speed V=30-100 km/h
The following three cases of ground-plan motorway guiding were taken into consideration:
- motorway in straight line, R=∞
- motorway in raidus R= 450 m
- motorway in radius R= 750m
Figure 3. Redirection of traffic across official passage in the median strip (2 traffic lanes)(1)
Table 2.: Passage lengths LP for different speeds and modelling elements (1)
V[km/h] / R
[m] / A
- /
Lp1 m.s.=3m straight line
/Lp2 m.s.=4m straight line
/Lp1 m.s.=3m R=450m
/ Lp2 m.s.=4m R=450m / Lp1 m.s.=3m R=750m / Lp2 m.s.=4m R=750m30 / 25 / 10 / 35,25 / 36,47 / 34,63 / 35,79 / 34,93 / 36,11
40 / 45 / 20 / 52,49 / 54,27 / 52,71 / 54,40 / 52,64 / 54,36
50 / 75 / 30 / 69,07 / 71,45 / 68,69 / 71,00 / 68,74 / 71,07
60 / 120 / 40 / 85,62 / 88,72 / 86,83 / 89,91 / 85,79 / 88,85
70 / 175 / 50 / 101,55 / 105,35 / 107,11 / 111,07 / 104,10 / 107,91
80 / 250 / 60 / 118,53 / 123,12 / 133,42 / 142,21 / 123,30 / 128,26
90 / 350 / 80 / 141,86 / 147,31 / - / - / 156,43 / 162,47
100 / 450 / 120 / 174,35 / 180,46 / - / - / - / -
Basic principles for passage design
The position of passages depends on ground-plan and longitudinal motorway position and on the position of facilities (viaducts, bridges, tunnels).
As operative length of a motorway section under construction amounts to approximately 5 km, distance between the passages in the median strip should be around 5 km. The practice has shown that maximum speed in passages should be limited to 80 km/h.
The following two passage types and one subtype have been established on the basis of the overall research and considerations(1):
· Type 1 – in lowland terrain
- passage length LP = 135 m, maximum speed limit V=80 km/h, possible crossing of two traffic lanes onto adjacent roadway, modelling of passages with circular turns of "S" bends R=350 m (in exceptional cases Rmin=250 m).
· Type 2 – in highland (mountainous) terrain
- passage length LP = 90 m, maximum speed limit V= 60 km/h, possible crossing of two traffic lanes onto adjacent roadway, modelling of passages with circular turns of "S" bends R=200 m
(in exceptional cases Rmin=120 m).
Subtype 2A – in highland terrain – in exceptional cases (it is not possible to ensure sufficient passage length)
- passage length LP = 55 m, maximum speed limit V=40 km/h, possible crossing of one
traffic lane onto adjacent roadway, modelling of passages with circular turns of "S" bends R=100 m (in exceptional cases Rmin=60 m).
The passage length in front of long tunnels (L ≥ 500 m) should be approximately 150 m.
ARRANGEMENT OF THE OFFICIAL PASSAGES
The research results have suggested that passages in the median strip of motorways should be built (1):
- in front of and behind nodes (min. 900 m)
- in front of and behind long bridges/viaducts (L ≥ 500 m)
- in front of and behind long tunnels (L ≥ 500 m)– minimum 150 m from portals
- between tunnels or viaducts built in a row
- on each 3-5 km on straight line sections of motorways.
It is recommended that emergency vehicles or vehicles for motorway maintenance use lateral exits and entrancees through wire fences, near overpasses or underpasses.
CONCLUSIONS AND RECOMMENDATIONS
The official passages in the median strips of motorways should be completely closed and intended for safe and proper traffic redirection onto opposite roadways in all weather condtions and situations. It is recommended that emergency vehicles use lateral passages near overpasses/underpasses.
Based on the analyzed issues, series of research and current situation in Croatia and certain European countries, the following conclusions are recommended:
· distances between passages on straight line motorway sections should be from 3 to 5 km;
· vehicle speed across passages should be limited to 80 km/h, i.e. 60 km/h (in exceptional cases 40 km/h, which must be specially elaborated);
· for motorways in lowland terrain passage lengths should be 135 m, and in highland terrain 90 m (V = 60 km/h);
· two uniflow traffic lanes should be planned for traffic redirection across passages onto adjacent roadways (in exceptional cases one);
· passages should be built in front of and behind nodes (min. 900 m) and long bridges/viaducts, tunnels (L ≥ 500 m).
LITERATURE
(1). Oblikovanje i razmještaj prolaza u razdjelnom pojasu autocesta, operative version, HAC/FPZ, Zagreb, 2005.
(2). Directive 2004/54/EC of The European Parliament on minimum safety requirements for tunnels in the Trans-European Road Network, EU Official Journal L 167, 2004.
(3). TEM Standards and recommended practice, (TEM/SRP) UNECE, Warsaw, Poland, 2002.
(4). Božičević J., Legac I.: Cestovne prometnice, FPZ, Zagreb, 2001.
(5). Handbuch für die Bemessung von Strassenverkehrsanlagen (HBS), Forschungsgesellschaft für Strassen- und Verkehrswesen, Köln, 2001.
(6). EN 1317 – 1...6 – Road Restraint Systems, 1998.
(7). Richtlinien für die Sicherung von Arbeitsstellen an Straβen (RSA),1995.
(8). NEN 5190- Safety barriers - Requirements for constituents and NEN 5191 - Safety barriers - Rules for execution , Netherlands, 1995.
(9). Highway Capacity Manual (HCM), Special Report 209, Transportation Research Board, Washington D. C., 1994.
(10). Projektovanie ciest a diaľnic , STN 73 6101, MDPTR SR, Slovakia, 1992.
(11). Richtlinien für passive Schutzeinrichtungen an Straβen (RPS), 1989.
(12). JUS.S.4.110,sl. list br.60/84. – Zaštitne ograde, čelične, 1984.
(13). Allgemeines Rundschreiben, Straβenbau Nr. 4/72, München, 1972.
(14). TSC 02.210 – Varnosne ograje, pogoji i način postavitve, Slovenija, undated.
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