ANNEX B SPECIFICATIONS FOR THE PROTECTION OF LEVEL CROSSINGS ) INTRODUCTION Definition: A level crossing arises from the intersection of a road with the railway. It then creates a problem, since the level crossing must be safely protected, supporting the development of traffic both on the road and the railway. To avoid collisions, continuity of road traffic is interrupted at a given time and for a certain period of time. To this end the following prevention devices are used, depending on the importance and danger of the crossing: ) Warning signs: Fixed road signs (diagonal struts) with the words "RAILROAD CROSSING" or "CAUTION TRAINS". 2) Warning signs: In addition to the diagonal struts, audio and light signals are added (flashing lights and bell sounds). 3) Fixed obstacles: swinging barriers to prevent vehicular traffic (when barriers are installed, you should also install audio and light signals as well as diagonal struts). 2 CHARACTERISTICS OF LEVEL CROSSINGS The general characteristics of level crossings can be grouped as follows: 2.) Geometric aspects: Within the geometric aspects, the following can be highlighted: road and track width, crossing angle of the road and railway (it must tend to be perpendicular to each other); crossing ramps, etc. 2.2) Characteristics of trains: The following aspects should be taken into account: top speed of trains on the section of track corresponding to the level crossing considered, trains stopping distance, maximum tonnage and maximum train set. 2.3) Characteristics of road vehicles: Design speed of the road that crosses the railway, braking distance of vehicles, vehicle weight, etc., must be taken into consideration. 2.4) Visibility: The "diamond visibility" of a level crossing is defined (Fig. XIV-), as the area at a distance d from the nearest rail measured by the axis of the road, (d = 30 m if the road is paved and d = 5 m if it is a rough road).
The other diagonal of the diamond visibility is determined by measuring from the axis of the level crossing a distance equal to 5v by the center of the track, where v is the maximum speed a train can circulate on the track (in km/h). The diamond visibility must be unobstructed to allow good visibility of the crossing for road vehicles and train drivers. Fig. : Outline of "diamond visibility" of a level crossing 3. Climatic factors: The following factors can negatively influence the perception of a train that is about to cross: reflections of the sun, foggy areas, (they impair visibility), wind or other sounds that prevent the acoustic perception of the approaching train or prevent hearing acoustic signals if any. 4. Pavement and enclosure protection: Level crossings must consider the compatibility of the road and railway that cross, that is why there is a number of track protection elements, like "periodically removable" pavements to allow mechanized track maintenance. 4.) Guardrails and check rails: they are side rails serving as protection to the main rails forming the railway rack. The check rails are the inner rails that protect the wheel flanges while the outer rails are guardrails. 4.2) Pavement: The pavement on the level crossing can be of different types, according to the preferences and resources of both managers of the railway infrastructure and the road or trail that crosses. b) Plates or precast concrete slabs (reinforced or prestressed) can be used, as well as wooden planks secured to the sleepers of the track by means of bolts (Fig. 2, a). This type of pavement has the advantage that it can be removed to repair the road below and then restored with the same elements. b2) Asphalt pavement (Fig. 2, b) has the disadvantage of segregating with heat and vehicular traffic; it must also be completely rebuilt in case of having to be removed to work on the railway below the overpass.
b3) Another kind of pavement can be made with concrete pavers (Fig. 2, c), which has the advantage of being easy to remove and reconstruct. b4) The "Holdfast" system (Fig. 2, d) uses high strength rubber panels, which can be removed and placed back. They are fixed to the sleepers by specially designed metal brackets. b5) Removable metal plates are also used with a supporting structure of steel profiles fixed to the sleepers with bolts or screws. a) Level crossing paved with concrete slabs or wooden planks b) Level crossing with asphalt pavement c) Level crossing with concrete paving stones pavement d) Level crossing with high strength rubber panel pavement ("Holdfast" system) Fig. 2: Types of pavements in level crossings
4.3) Crosswalks: if it is a level crossing in an urban area where pedestrian traffic may exist, a safe crossing for pedestrians should be provided, so immediately after the sidewalk, concrete tiles are placed on the track. But as a preventive measure, turnstiles are installed on the railroad access area to warn pedestrians that they are entering a danger zone (Fig. 3, a). 4.4) Fence and "cattle guard" grids: The strip of railway must be closed by a fence or dividing wall, as the perimeter fence is broken at the intersection of the road with the railway, entry of animals to the strip of track must be avoided, so for that purpose cattle guard grids are used, which are fixed to the sleepers by means of bolts (Fig. 3, b). a) Level crossing with turnstile and b) Level crossing with fence and "cattle guard" crosswalk grids Fig.3: Additional protection systems at level crossings 3 ) SIGNALING AND PROTECTION OF LEVEL CROSSINGS The protection of a level crossing depends on its importance and the risks of accidents, which is determined by calculating its HAZARD INDEX. There are three main types of protection, according to the danger of the level crossing: 3.) FIXED SIGNALING: DIAGONAL STRUTS Diagonal struts are universally used with the words "RAILROAD CROSSING" or "CAUTION TRAINS" (Fig. 4, a). These signs are painted with reflective paint, allowing viewing at night. Universally used colors are: yellow-black; white-black; white-red. 3.2) AUDIO AND LIGHT SIGNALS ("FLICKERING") These devices are light sources that emit flashes intermittently, along with acoustic elements announcing the proximity of a train, which are usually accompanied by diagonal struts (Fig.4, b).
Like the automatic barriers, these mechanisms are triggered by trains passing through magnetic or electric detectors (track circuits), located at a certain distance from the level crossing. 3.3) BARRIERS In general level crossings with barriers also have diagonal struts as well as audio and light signals. Barriers (Figures 4, c and d) can be operated in three ways: a) Manually b) Semi-automatically c) Completely automatic a) Level crossing protected with diagonal struts b) Level crossing protected with flickering signs c) Level crossing protected with barriers d) Level crossing protected with barriers Fig. 4: Level crossings protection systems 3.3.) Manually operated barriers This type of barriers consist of a column holding the arm, with a counterweight in the opposite end. In this case the barrier is operated through a winch mechanism by a worker called "level crossing attendant". It has the disadvantage of having a worker exclusively for the operation of the barrier.
The operator may be permanent (24 hours a day throughout the year); full-time (all year, but not 24 hours a day) and seasonal (can be full-time or permanent, but only during seasonal work). 3.3.2) Interlocked or semi-automatic barriers They can be operated from local or central control stations (centralized control). Interlocked barriers can have two types of operations: mechanical or electrical. Mechanical operation is carried out from the local control station via a system of ropes, pulleys and levers transmitting movement to the barriers. For electric operation, there is a set of levers; engine transmitter; clutch; switches; relays; etc. In many cases operation (mechanical or electrical) is complemented by a CCTV installed in the control room to facilitate the visibility of the level crossing. The barriers with electric operation have track circuits, using relays connected to the control room, so that the worker presses a button to operate a motor that lifts and lowers the barrier. In these cases, the barriers have an electrical or electronic interlocking linked to the signals (which may be two or three points), when the operator "opens" the "green light" signal to a train going through the level crossing, the barriers must be low for the interlocking to enable the green light, otherwise (if the barriers did not lower), the interlock will not give the green light and the red light signal will remain. The electrical interlocks are actuating devices that check the position of the barriers (low or lifted). The barriers have "warning" signs for drivers showing the status of the barriers, (if the barrier is in the correct position, that is, low when the train passes, it has white or green appearance, which means that the system is operating correctly, however, if the barrier is lifted, it means it is not working and appearance will be red, so the train must stop before the level crossing and continue once the driver has made sure there are no upcoming highway vehicles crossing, or otherwise, the driver must pass "with caution". 3.3.3) Automatic barriers They are driven by detectors located at a certain distance from the level crossing (depending on the top speed) when the train passes through the point of the railway where the first detector is located, the mechanism of the barriers start operating, ending when the train has passed the level crossing (item 2). Detectors can operate by magnetic or electrical detection. Let us suppose that the first detector (either electric or magnetic) is located in point, when the train passes through point the warning system is activated (the bells and flashing red lights are activated), 20 seconds later (warning time), the barrier starts to lower (the time it takes to lower the arm is approximately 5 seconds). When the last axis of the caboose of the train goes through item 2 (where the second detector or detector output is located) the circuit is closed, the arm is lifted and the flashing lights and bells are turned off. The total time is about 35 seconds, from the moment the flashing lights are turned on and the ringing bells go off until the train passes, plus the time it takes for the train to go through the level crossing until the barriers are lifted. There is also a third detector (item 3) for the trains running in the other direction (because the system is symmetrical with respect to the level crossing).
Fig. 5: Single track automatic barrier drive control Fig. 6: Double track automatic barrier drive control The most common option is to install isolated joints on both sides of the level crossing, creating an "island circuit" (Fig. 5 and 6), in this way the barriers begin to be lifted once the last wagon of the train passing releases the island circuit (in the case of single tracks, directional relays must be installed). XIV - 3.3.4) Components of barriers Both automatic and semiautomatic barriers have almost all of the same mechanisms, differing only by the actuators, being able to even move from one system to another. They consist of a column located on the side of the road (off the edge of the shoulder), anchored in solid concrete (Fig. 7). The arm of the barrier is mounted on the column and articulated to allow up and down movement, with a counterweight at the other end (Fig.8). Fig. 7: Level Crossing barrier Fig. 8: Level crossing half-barriers scheme The arms can be designed to completely cover the roadway (complete barriers) or as entry half-barriers in each direction, in which case it is advisable to install an edge in the middle of the road, to separate both directions of travel. The arms can be galvanized, wood or polyethylene fiberglass pipes, painted with reflective paint on both sides with alternating bands of two colors, which can be: blackwhite; red-white; black-yellow; etc.
The colors are regulated by the various administrations, particularly in Uruguay, the black-yellow combination was used until a short time ago, which has been recently amended by that of black-white in the conference of Transport Ministers of MERCOSUR. The drive system of the barrier comprises a 2 v DC motor, a set of reduction gears and arm position cams. One of the gears is integrally attached to the arm to allow up or down movements. Other elements of the drive mechanism are connecting terminal blocks, a lowering control resistor, switching relays, a brake system and position limits, both when the barrier is low and lifted. The motor can be powered by electricity, batteries, solar or wind energy. XIV - 4) FLYOVERS When the density of rail and road traffic is very high, the chances of a collision at the level crossing increase, thus increasing the danger. In this kind of situations it is necessary to build crossings at different levels. Depending on the topography, urban and landscape features, the split-level crossing can be an underpass or an overpass (Fig. ). Route Nº 5 overpass on the road at Km 3 of the Rivera (Florida) Line. José Batlle y Ordoñez underpass at Km 8.5 of the Rivera Line (Montevideo). Fig. : Split-level crossings
5) DETERMINATION OF LEVEL CROSSINGS PROTECTION - HAZARD INDEX Determination of a level crossing hazard index (P) is done using the following formula: Where: T is the number of trains in the busiest 2 hours. V is the number of vehicles in the busiest 2 hours. F, F2, F3 and F4 are the visibility factors. is the angle of crossing of the road with the railway. b is a parameter determined by the values in Table XIV-. To find the visibility factors, the following must be taken into consideration: the sections of road visible on both sides by an observer at the level crossing, 5 m from the first track on unpaved roads and 30 m when the road is paved or improved and.50 m above the pavement (visual height of a conductor located inside of a vehicle in the road crossing the railway). Visibility factors are calculated with the following formula: F l i 5.v where v is the top train speed in km/h. l i is the visible railway length over a distance equal to 5.v in each of the four directions. It follows that when there is clear view, that is, no obstacles, the visibility factor is one. Table : Determining parameter b according to the following factors: Gradients totaling up to 8 % in both sides Up to 30 % up to 4 % in only one side Up to 5 % Narrow Crossing Up to 0 % Side roads ending within 20 m from the level crossing Up to 5 % for two tracks Up to 0 % Multiple tracks for three tracks Up to 20 % for four or more tracks Up to 30 % Reflections of the sun Up to 5 % Once the hazard index value (P) is found according to the result obtained by the above formula, the following type of protection is established: ) If P 2,000: the level crossing must be protected with prevention signs of the diagonal strut type. 2) If 2,000 P 50,000: the level crossing must be protected with audio and light signals. 3) If P 50,000: the level crossing must be protected with barriers. 4) If P 50,000: it is recommended to build a split-level crossing.
5.) EXAMPLES OF CALCULATION OF HAZARD INDEX Example Nº: Given the level crossing in Figure 2 below: Fig. 2: Level crossing at right angles with an outer wall The number of trains in the busiest 2 hours (T) is 87 trains, the number of vehicles in the busiest 2 hours (V) is 550 vehicles, and the train speed is 60 km/h. The geometry of the zone indicates that the half-width of the road (a) is 5 m, and the improved or paved road is 30 m long. The location of the observer at point A is.50 m. The visible lengths of track in this case are: l = 50 m for having the visibility obstructed by the outer wall, and L2 = L3 = L4 = 5.V = 5 x 60 = 300 m for having clear view. Therefore, the visibility factors are: F = 50/300 = 0.67, for obstructed visibility, and F 2 = F 3 = F 4 = 300/300 =, for having clear view. So, the hazard index is: Therefore this level crossing must be protected by barriers. Example Nº2: Now let us consider the level crossing in Figure 3 below: Fig. 3: Level crossing at right angles with a house and a tree on a corner
The number of trains in the busiest 2 hours (T) is 32 trains, the number of vehicles in the busiest 2 hours (V) is 80 vehicles, and the train speed is 70 km/h. The geometry of the zone indicates that the half-width of the road (a) is 5 m, and the improved or paved road (d) is 30 m long. The location of the observer at point A is.50 m. The visible lengths of track in this case are: l 4 = 24 m and l 5 = 0 m for obstructed visibility, and l = l 2 = l 3 = 5.V = 5 x 70 = 350 m for clear view. Therefore, the visibility factors are F = F 2 = F 3 = 350/350 = for having clear view, and F 4 = (24 + 0) / 350 = 0.097 for obstructed visibility. So, the hazard index is: Therefore this level crossing must be protected by diagonal struts. Example Nº3: Given the level crossing in Figure 4 below: Fig. 4: Skew level crossing with clear view The number of trains in the busiest 2 hours (T) is 65 trains, the number of vehicles in the busiest 2 hours (V) is 380 vehicles, and the train speed is 80 km/h. The geometry of the zone indicates that the half-width of the road (a) is 7.50 m, and the paved or improved road (d) is 5 m long. The location of the observer at point A is.50 m and the crossing angle ( ) is 70º. Visible railway lengths in this case are l = l2 = l3 = l4 = 5.V = 5 x 80 = 400 m for having clear view. Therefore, visibility factors are F = F2 = F3 = F4 = 400/400 = for having clear view. So, the hazard index is: Therefore this level crossing must be protected by audio and light signals.
Example Nº4: Given the level crossing in Figure 5, ending in a side road: Fig. 5: Skew level crossing on a side road The number of trains in the busiest 2 hours (T) is 70 trains, the number of vehicles in the busiest 2 hours (V) is 420 vehicles, and the train speed is 70 km/h. The geometry of the zone indicates that the half-width of the road (a) is 5 m and the improved or paved road (d) is 30 m long. The location of the observer at point A is.50 m. The crossing angle ( ) is 45º. Visible railway lengths in this case are l = l2 = l3 = l4 = 5.V = 5 x 80 = 400 m for having clear view. Therefore, visibility factors are F = F2 = F3 = F4 = 400/400 = for having clear view. So, he hazard index is: To calculate b, the following are considered: Ramp on one side (3.34%) 2.5% Side road 0 % Double track 0 % Giving a total of 32.5%, then b = 4,577.88 x 0.325 = 3,52.8 so: P = 4,577.88 + 3,52.8 = 55,090.69. Therefore this level crossing must be protected by barriers.
5.2) INDIVIDUAL CASES TO DETERMINE THE HAZARD INDEX There are many cases of road crossings with the railway, in which the level crossing serves a road that crosses the railway at right angles, but its direction before getting to the railway is parallel to it (Figure 6). Fig. 6: Level crossing at right angles to a road that runs parallel to the railway To find the hazard index in cases like these, point (A) of the observer location is determined by measuring the distance from the first track already established in 5 or 30 m in the direction of the road. Then angle ABC = formed by the intersection of the axis of the road with the first rail, point A and the extension of the first rail, is measured (Figure 7). Fig. 7: Determination of the hazard index of a level crossing at right angles to a road that runs parallel to the railway The hazard index is then calculated as if the road crossing with the track was skewed at a angle.