WO1999036631A1

WO1999036631A1 - Improvements to a semirigid, position-correctable, collision-energy-dissipating, guardrail

Info

Publication number: WO1999036631A1
Application number: PCT/IT1999/000007
Authority: WO
Inventors: Mariano Pernetti; Giovanni Battista De Martino; Cesare Iacoangeli
Original assignee: Ilva Pali Dalmine S.R.L.
Priority date: 1998-01-19
Filing date: 1999-01-19
Publication date: 1999-07-22
Also published as: AU2073199A; ITTO980044A1; EP1058755A1

Abstract

The guardrail (1) has a rail (5) connected to each post (3) by a spacer (13) and an energy dissipator (21), in which the spacer (13) carries two cam slots (27, 28) engaged by two pins (29, 30). The spacer (13) has a horizontal rib (20) located between the two slots (27, 28) and housed inside a rib (35) on the dissipator (21), which also has a further two horizontal ribs (33). The pins (29, 30) are of equal diameter and also engage two identical openings (11, 12) in a release body (41) movable telescopically inside the post (3). The openings (11, 12) are defined by two partitions (14, 49) which are sheared simultaneously by the pins (29, 30). And the guardrail (1) also has a wheel rail (50) carried by a spacer element (51) having an opening (56) of constant width, by which the spacer element slides over a pair of different-diameter bolts (57, 57') fitted to the post (3).

Description

IMPROVEMENTS TO A SEMIRIGID, POSITION-CORRECTABLE, COLLISION-ENERGY-DISSIPATING, GUARDRAIL TECHNICAL FIELD The present invention relates to improvements to a semirigid, position-correctable, collision-energy- dissipating guardrail. BACKGROUND ART

Guardrails of the above type are known in which a shaped rail is connected to a number of posts by means of respective fastening assemblies, each comprising a spacer and a collision energy dissipator.

In one known type of guardrail, the spacer is connected to the post by means of a pair of cam slots cooperating with a pair of pins, and which provide for substantially rigid connection at the initial vehicle collision stage, and for position correcting the rail at a subsequent collision stage via rotation and translation of the post and spacer. One of the pins is sheared at a further collision stage, and the spacer comprises a telescopically movable body which, at the final collision stage, is released from the post. This type of guardrail is highly effective in preventing vehicles from running off the road, and, as confirmed by test results, provides for a high degree of control energy, with relatively little acceleration of light vehicles in the course of collision. On the other hand, it is relatively heavy, on account of at least the spacer and dissipator having to be made of extremely thick sheet metal, and cost is increased by the shear pin having a calibrated diameter. Moreover, each post of the above known guardrail is hinged by a slot and pin connection to a spacer element of a wheel rail; the slot tapers to create a certain amount of resistance to the sliding movement of the pin during collision; and the spacer element and wheel rail both have a C-shaped section, and are connected to each other by a vertical bolt.

The post-wheel rail connection also involves several drawbacks. In particular, the C-section wheel rail is relatively heavy and rigid; the tapering slot is fairly expensive to produce and tends to damage the sliding pin; and, in the case of a traffic-dividing guardrail, in which each post is fitted with a double spacer for two opposite rails, the post fails to provide for effectively distributing part of the collision energy on the rails to the adjacent posts. DISCLOSURE OF INVENTION It is an object of the invention to provide a semirigid guardrail which, while maintaining a high degree of vehicle control by maintaining the height and vertical position of the rail even in the event of substantial displacement, exploits the ductility of the materials to dissipate a greater amount of collision energy, and provides for eliminating the aforementioned drawbacks typically associated with known guardrails. In particular, it is a first object of the invention to provide a guardrail in which both the spacer and the dissipator are sufficiently rigid and relatively lightweight, while at the same time maintaining a maximum degree of efficiency.

This object is achieved by the semirigid, position- correctable, collision-energy-dissipating guardrail according to the invention, which comprises a number of posts, and at least one shaped rail connected to each of said posts by a respective fastening assembly comprising an energy dissipator located between said rail and a spacer carried by said post; said spacer being connected to said post by a group of cam guides cooperating with a group of engaging elements; said group of cam guides being such as to provide for a substantially rigid connection at an initial stage in the collision of a vehicle, and for a position correction of said rail at a subsequent stage in said collision; and is characterized in that said spacer comprises at least one strengthening rib located between said cam guides .

It is a further object of the invention to provide a guardrail in which the post shows no noticeable local stability phenomena during collision of the vehicle. It is also an object of the invention to eliminate shearing of the connecting pin to release the rail from the post.

This further object is achieved by the semirigid guardrail according to the invention, wherein the cam guides are defined by shaped slots on said spacer; said engaging elements being defined by pins carried by said posts and engaging a body connected telescopically to a top portion of said post; said body permitting release of said rail from said post at a final stage in said collision; and said guardrail being characterized in that said pins each engage a corresponding opening in said body; each of said openings being defined by a partition which is sheared by the corresponding pin at said final stage . It is a further object of the invention to provide a guardrail wherein the wheel rail is cheap to produce and is highly plastic in the event of vehicle collision. It is also an object of the invention to eliminate deterioration of the connection between the spacer element and the post .

This further object is achieved by the semirigid guardrail according to the invention, wherein said each of said posts is also connected to a spacer element fitted with a wheel rail extending parallel to and beneath said shaped rail; said guardrail being characterized in that said spacer element comprises a longitudinal opening of constant width and engaging a pair of elements fitted to said post so as to position said opening horizontally and to slide with respect to said opening in the event of collision by vehicle wheels .

Finally, it is a further object of the invention to enable each post to discharge part of the collision energy onto the adjacent posts.

This further object is achieved by the semirigid guardrail according to the invention, wherein each spacer comprises two opposite vertical edges; said guardrail being characterized in that one edge of the spacer of a first of said posts and the opposite edge of the spacers of the adjacent posts are connected by a diagonal reinforcing member. BRIEF DESCRIPTION OF THE DRAWINGS Two preferred, non-limiting embodiments of the invention will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a front view of a first preferred embodiment of a semirigid guardrail featuring the improvements according to the invention;

Figure 2 shows a top plan view of the Figure 1 guardrail; Figure 3 shows a larger-scale section along line III-III in Figure 1;

Figures 3A and 3B show larger-scale sections along lines A-A and B-B in Figure 3; Figure 4 shows a larger-scale top plan view of Figure 3 ;

Figure 5 shows a partial view in perspective of the Figure 3 guardrail;

Figure 6 shows a larger-scale exploded view in perspective of a detail in Figure 5;

Figure 7 shows a larger-scale view of a detail in Figure 1 ;

Figure 8 shows a variation of the Figure 7 detail;

Figures 9, 10, 11 show layouts of three components of the guardrail;

Figure 12 shows the same view as in Figure 3 of a further embodiment of the invention;

Figure 13 shows a larger-scale top plan view of Figure 12; Figure 14 shows a top plan view of a portion of the Figure 12 guardrail;

Figure 15 shows a larger-scale front view in perspective of a detail in Figure 14. BEST MODE FOR CARRYING OUT THE INVENTION Number 1 in Figures 1 and 2 indicates as a whole a semirigid guardrail of the type installed along the edge of a road 2. Guardrail 1 comprises a number of posts 3; and a shaped rail 5 extending crosswise to posts 3 and connected to each post by a fastening assembly 6. More specifically, rail 5 (Figures 3 and 4) is a known type comprising three ridges separated by two grooves 4. Each post 3 is defined by a metal channel section with the concavity facing one of the two adjacent posts 3; each channel section comprises two lateral walls 7, and an intermediate wall 8 perpendicular to rail 5; each wall 7 terminates with a partial wall 8 ' parallel to wall 8; each post 3 is fitted vertically into the ground by a bottom portion 9, and comprises a top end portion 10 in which assembly 6 is fitted; wall 8 of portion 10 has two axial openings 11 and 12 (see also Figure 6) separated by a partition 14; and assembly 6 comprises a spacer 13 carried by post 3, and an energy dissipator 21 located between rail 5 and spacer 13.

More specifically, spacer 13 comprises two parallel plates 16 (see also Figure 5) fitted respectively to wall 8 and to partial walls 8 ' of post 3 , and each having a top and bottom tab 17, 18 extending outwards. Spacer 13 is connected to post 3 by a respective group of cam guides associated to spacer 13 and cooperating with a group of engaging elements associated to post 3. The cam guides are defined by two shaped slots 27 and 28, and the engaging elements by two pins or bolts 29 and 30 which slide inside slots 27 and 28. More specifically, each plate 16 comprises two slots 27, 28 separated vertically. Bolts 29 and 30 extend perpendicularly to plates 16 and also engage in sliding manner openings 11 and 12 in wall 8 of post 3, and two vertically aligned slots 38 and 39 (Figure 6) formed in a wall 40 of a body 41 connected telescopically to top portion 10 of post 3. To prevent jamming, bolts 29 and 30 are connected by two spacer plates 41a (Figures 3, 3A, 5) . Body 41 (Figure 6) has a U-shaped section comprising two walls 44 on either side of wall 40, is positioned with wall 40 in correspondence with partial walls 8' of post 3, and slides inside portion 10 where it is retained frictionally by two coaxial bolts 42 tightened by respective nuts . Each bolt 42 engages a hole formed in the corresponding wall 7 of post 3, and an open-bottomed longitudinal opening 43 formed in the corresponding lateral wall 44 of body 41.

Slots 27 and 28 (Figure 3) are so formed as to provide for substantially rigid connection at the initial stage in the collision of a vehicle with rail 5, and for position correcting rail 5, via rotation and translation of post 3 and spacer 13, at a subsequent collision stage. At the final collision stage, body 41 is released from post 3 to enable release of rail 5 from post 3 , substantially as described in Italian Patent Application TO94A000822 filed by CENTRO ACCIAI S.P.A. Guardrail 1 also comprises a tie defined by a metal strip 45, which is connected by a U-shaped bracket 46 fitted to the rear edges of the two plates 16 of each spacer 13. Finally, guardrail 1 also comprises a wheel rail 50 extending parallel to and below shaped rail 5, and which is fitted with a spacer element 51 connected to post 3 as described later on.

According to the invention, spacer 13 is defined by a sheet metal plate 15, a layout of which is shown in Figure 9, and which comprises two lateral portions and a narrower central portion. Plate 15 is bent into a U so that the lateral portions form the two plates 16, from which tabs 17 and 18 are bent, and so that the central portion forms an intermediate wall 19 defining the front edge of spacer 13. The two plates 16 are bolted in between with two contrasting spacer sleeves 22 close to wall 19, and with a further sleeve 22 at bracket 46.

A strengthening rib 20, the axis of which is shown by the dot-and-dash line in Figure 9, is formed along the whole length of plate 15, projects outwards of plates 16 and wall 19, is located between slots 27 and 28, at the same distance from the bottom end of each upper slot 27 and the top end of each lower slot 28, and provides for increasing the rigidity of plates 16 as bolts 29 and 30 (Figure 3) slide along slots 27 and 28 in the event of collision, and for ensuring correct position correction of rail 5. Dissipator 21, in turn, is defined by a further sheet metal plate 23, a layout of which is shown in Figure 10, and which is bent into a U to form two lateral walls 24 connected by rounded edges to an intermediate wall 25. Plate 23 comprises a horizontal opening 26 extending at least the whole length of intermediate wall 25; a pair of holes 31 for bolted connection to the two grooves 4 of rail 5 (Figures 3, 4, 5); and two pairs of short slots 32 for connection to spacer 13 at the two sleeves 22 adjacent to wall 19.

Dissipator 21 comprises at least one horizontal rib

33 extending the whole length of plate 23. More specifically, dissipator 21 comprises two horizontal ribs 33, the respective axes of which are shown by the dot- and-dash lines in Figure 10, and which project outwards of dissipator 21 and are each located between opening 26 and a respective hole 31. Each groove 4 comprises a row of slots 37 (Figure 5) with the same spacing as posts 3.

The two ends of opening 26 are closed by two closing portions 34 (Figure 10) , each of which comprises a further horizontal strengthening rib 35, the axis of which is indicated by a dot-and-dash line in Figure 10. Each rib 35 is so located as to house, in its own cavity, rib 20 of corresponding plate 16, and so further increase the rigidity of spacer 13. Opening 26 closed by portions

34 provides for improving the vertical position of dissipator 21 in the event of collision, and ribs 33 and 35 enable the dissipator to be less deformable with respect to the shearing action between spacer 13 and rail 5.

Rail 5 is defined by segments 5' and 5" (Figures 1 and 7) connected by superimposing end portions 47 of two adjacent segments 5', 5". Each end portion 47 comprises a further pair of slots 37 formed in grooves 4; and two rows of six holes 36 for respective connecting bolts 48. Holes 36 are formed in the sides of the three ridges of segments 5', 5"; and the distance between the center of each slot 37 and the end edge of portion 47 is substantially equal to the distance D between the centers of the two slots 37.

The two pairs of central holes 36 in the two rows are spaced further apart than the other pairs of holes 36. More specifically, the two central holes 36 in each row are so located that the distance between the respective centers and the outer edge of one of the two connected portions 47 is substantially equal to the depth P of groove 4 (Figure 3) , i.e. to the distance between the plane of slots 37 and the plane tangent to the top of the ridges of rail 5.

Advantageously, in the case of a standard 508 mm wide rail with a total extended width of 736 mm, the distance D between the centers of slots 37 is approximately 194 mm; the distance between the center of each slot 37 and the edge of portion 47 may be 190 mm; the depth P of groove 4 is approximately 81 mm; and the distance between the centers of outer holes 36 of the central rows and the edge of portion 47 may be 82 mm.

The centers of the other four pairs of holes 36 may be 100 mm apart, so that the centers of the four holes 36 in the outer row are 58 mm from the edge of portion 47, and are located along a vertical line L between and substantially equidistant with respect to a vertical line through the centers of slots 37 and the vertical line through the centers of the other two holes 36.

In the Figure 8 variation, holes 36 in each row are all located at the same distance from the outer edge of portion 47; which distance, in the case of the outer row, may be substantially equal to depth P of groove 4 , and may advantageously be 82 mm.

Both the Figure 7 and 8 variations of slots 37 and holes 36 have been calculated experimentally, and the high degree of efficiency of the connection confirmed by testing. According to a further aspect of the invention, the top opening 11 (Figures 3 and 6) of portion 10 of post 3 is closed at the top by a partition 49 of the same width as partition 14; and openings 11 and 12 are the same length and width, and bolts 29 and 30 of the same diameter to simplify construction of guardrail 1. Bolts 29 and 30 of the same diameter also enable body 41 to slide inside portion 10 of post 3 in the event of low- energy collision, e.g. by a car.

Moreover, each of the two spacer plates 41a (Figures 3 and 3A) is located inwards of respective plate 16, and is therefore guided perfectly between plate 16 and respective wall 8, 8' of post 3; and each post 3 comprises two braces or plates 60 (Figures 3 and 3B) welded to the inside of partial walls 8 ' of the portion 9 concreted into the side of road 2. Plates 60 may advantageously be spaced about 200 mm apart, with the top plate 60 located 50 to 150 mm from the surface of road 2, and provide for strengthening, for drastically reducing local instability, and for better exploiting the resisting section of post 3. Bolts 29 and 30 provide for simultaneously shearing partitions 14 and 49 in the event of impact exceeding a predetermined energy level, e.g. in the event of a heavy vehicle colliding with the rail. In which case, body 41 is expelled from portion 10 of post 3, so that rail 5 is released from post 3 together with dissipator 21 and spacer 13.

According to a further aspect of the invention, wheel rail 50 (Figures 3 and 5) is defined by a flat bar, which is lighter than a channel section of equal resistance and is more plastic in the event of collision by a car; and spacer element 51 is defined by a third sheet metal plate 52, a layout of which is shown in Figure 11. Plate 52 comprises a narrow portion, which is bent 90° to form a tab 53 to which wheel rail 50 is fitted by means of a horizontal bolt 54. The rest of plate 52 is bent into a U, and comprises an intermediate wall 55 having a longitudinal opening 56 of constant width and of a length equal to about half the length of wall 55.

Opening 56 is engaged by two bolts 57, 57', which are fitted through two short vertical slots 58 in wall 8 of post 3, are fixed by means of respective nuts to position the axes of bolts 57, 57' adjustably in substantially the same horizontal plane, and provide for holding opening 56 and therefore spacer element 51 in a horizontal position. Bolt 57 closest to wheel rail 50 is smaller in diameter than bolt 57 ' and is sheared in the event of impact on the wheel rail exceeding a predetermined energy level. When struck by the wheel of a car, opening 56 of element 51 slides over bolts 57, 57', so that wheel rail 50 remains level with bolts 57, 57'.

Conversely, when struck by the wheel of a heavy vehicle, opening 56 of element 51 first slides over bolts 57, 57', and eventually shears bolt 57, so that element 51 is permitted to rotate with respect to post 3, and, on account of the diameter of the heavy-vehicle wheel, is dragged downwards to prevent the wheel from jamming between wheel rail 50 and road 2. In a further embodiment of the invention, the guardrail 61 (Figures 12-14) is a traffic-dividing type comprising two shaped rails 5 on either side of post 3, and two corresponding wheel rails 50. Post 3, in this case, comprises a double spacer 63 defined by two parallel plates 66, each having two bent tabs 17, 18 and two opposite vertical edges 64; the two plates 66 are connected at each pair of edges 64 by a channel section 65, between the lateral walls of which two sleeves 22 are inserted; spacer 63 comprises two opposite dissipators 21 identical to those of guardrail 1; and each dissipator 21 is connected at one end to plates 66 and to channel section 65 by means of two bolts, and at the other end to the corresponding rail 5 by means of a third bolt . Each plate 66 has two cam slots 67 and 68 engaged by bolts 29 and 30 in the same way as slots 27 and 28 in Figure 3; a rib 62, similar to rib 20, is provided between slots 67 and 68; each slot 67, 68 has a top end 69, 70 shared by the two arms of slot 67, 68 associated with respective rails 5; and the two arms extend downwards and are symmetrical with respect to a common vertical line .

Body 41 comprises a rectangular antijamming plate 71 having a central hole housing top bolt 29. In the event of collision with one of rails 5, antijamming plate 71 prevents pin 29 from engaging the branch of slot 67 associated with the other rail 5. The two wheel rails 50 are again each defined by a flat bar connected to a respective spacer element 51, 51'; spacer element 51' has a slightly smaller C-shaped section so as to be insertable inside spacer element 51; both spacer elements 51, 51' are connected simultaneously to post 3 by two bolts 57, 57', which, nevertheless, still have different diameters; and bolt 57 is sheared in the event of a heavy vehicle colliding with either the adjacent or the opposite wheel rail 50; in both of which cases, the engaged wheel rail 50 is dragged downwards by the vehicle wheel.

According to a further aspect of the invention, a diagonal reinforcing member 72 (Figures 14 and 15) is provided at edges 64 of spacers 63. More specifically, each diagonal member 72 is defined by a flat bar having an opening 73 of a length ranging from a quarter to a third of the total length of the bar, and which provides for exploiting the plasticity of diagonal member 72 along the whole length of the member. Diagonal member 72 has two perforated ends 74, which are bent at an angle, are housed inside opening 26 of each dissipator 21, and are fitted by means of a bolt between the intermediate wall of one channel section 65 of one post 3 , and the intermediate wall of the other channel section 65 of the adjacent post 3. Diagonal member 72 provides for discharging part of the collision energy on one post 3 onto the adjacent posts 3. The advantages, as compared with known guardrails, of the guardrail according to the invention will be clear from the foregoing description. In particular, ribs 20, 62 and 33, 35 on spacer 13, 63 and on dissipator 21 provide for strengthening plates 16 and 66 and dissipator 21 itself, for reducing the weight of the guardrail, and for preventing buckling when position correcting the rail following collision. Moreover, equal-diameter bolts 29 and 30 simplify construction of the guardrail and enable simultaneous shearing of partitions 14 and 49; constant- width opening 56 and different-diameter bolts 57 and 57' enable spacer element 51 to simply slide on post 3 in the event of impact by a car, and to rotate in the event of impact by a heavy vehicle; and, finally, diagonal member 72 provides for discharging part of the collision energy on one post 3 onto the adjacent posts 3.

Clearly, changes may be made to the guardrail as described herein without, however, departing from the scope of the accompanying Claims. For example, strip 45 of guardrail 1 may be replaced by a diagonal member similar to member 72 and fitted to wall 19 of the spacer and to bracket 46; changes may be made to the connection of segments 5', 5" of rail 5; and rail 5 may comprise a different number of ridges .

Claims

1) A semirigid, position-correctable, collision- energy-dissipating guardrail comprising a number of posts (3) , and at least one shaped rail (5) connected to each of said posts (3) by a respective fastening assembly (6) comprising an energy dissipator (21) located between said rail (5) and a spacer (13, 63) carried by said post (3); said spacer (13, 63) being connected to said post (3) by a group of cam guides (27,28; 67,68) cooperating with a group of engaging elements (29, 30) ; said group of cam guides (27,28; 67,68) being such as to provide for a substantially rigid connection at an initial stage in the collision of a vehicle, and for a position correction of said rail (5) at a subsequent stage in said collision; characterized in that said spacer (13, 63) comprises at least one strengthening rib (20, 62) located between said cam guides (27,28; 67,68).

2) A guardrail as claimed in Claim 1, wherein said group of cam guides (27,28; 67,68) comprises at least two cam slots (27,28; 67,68) spaced vertically; characterized in that said strengthening rib (20, 62) extends in a horizontal direction between said two cam slots (27,28; 67,68) . 3) A guardrail as claimed in Claim 2, wherein each of said two cam slots (27,28; 67,68) has a top end and a bottom end; characterized in that said strengthening rib (20, 62) is located between and equidistant with respect to the top end of the bottom cam slot (28, 68) and the bottom end of the top cam slot (27, 67) .

4) A guardrail as claimed in Claim 2 or 3 , wherein said spacer (13) is defined by a sheet metal plate (15) bent into a U and enclosing said post (3) ; said sheet metal plate (15) forming two lateral plates (16) and an intermediate wall (19) ; and each of said lateral plates (16) comprising two cam slots (27, 28); characterized in that said strengthening rib (20) extends the whole length of said sheet metal plate (15) .

5) A guardrail as claimed in Claim 4, wherein said rail (5) is of the type comprising three ridges separated by two grooves (4) ; characterized in that said dissipator (21) is defined by a further sheet metal plate (23) bent into a U and having two lateral walls (24) connected to said lateral plates (16) , and an intermediate wall (25) connected to said grooves (4) .

6) A guardrail as claimed in Claims 3 and 5, characterized in that said lateral plates (16, 66) are spaced by at least two spacing members (22) ; said lateral walls (24) being connected to said lateral plates (16, 66) at said spacing members (22) .

7) A guardrail as claimed in Claim 6, characterized in that said dissipator (21) comprises at least one horizontal rib (33) extending the whole length of said further sheet metal plate (23) . 8) A guardrail as claimed in Claim 6, characterized in that said further sheet metal plate (23) comprises a horizontal opening (26) extending at least the whole length of the respective intermediate wall (25) ; said dissipator (21) comprising two horizontal ribs (33) , each located between said horizontal opening (26) and a respective hole (31) for connection to one of said grooves (4) ; said horizontal ribs (33) extending the whole length of said further sheet metal plate (23) . 9) A guardrail as claimed in Claim 8, characterized in that said lateral walls (24) comprise two closing portions (34) closing the ends of said horizontal opening

(26) ; said closing portions (34) each having a respective reinforcing rib (35) . 10) A guardrail as claimed in Claim 9, characterized in that each of said reinforcing ribs (35) of said lateral walls (24) is so located as to house a portion of the strengthening rib (20, 62) of said lateral plates (16, 66) . 11) A guardrail as claimed in one of Claims 6 to

10, wherein said rail (5) is defined by segments (5', 5") connected to one another by superimposing an end portion

(47) of two adjacent segments (5', 5"); said end portion

(47) being positioned with a pair of slots (37) in said grooves (4) for connection to said dissipator (21) ; characterized in that the center of each of the slots (37) in said end portion (47) is located, with respect to the end edge of said end portion (47) , at a first distance substantially equal to the distance (D) between the centers of the slots (37) in said end portion (47) .

12) A guardrail as claimed in Claim 11, wherein each of said end portions (47) comprises two rows of holes (36) ; characterized in that at least some of said holes (36) in one of said rows are located, with respect to the end edge of one of said end portions (47) , at a second distance substantially equal to the depth of said grooves (4) .

13) A guardrail as claimed in Claim 12, wherein said holes (36) are formed in the sides of said ridges; characterized in that the holes (36) in one of said rows are all located at said second distance from the end edge of said end portion (47) .

14) A guardrail as claimed in Claim 12, wherein said holes (36) are formed in the sides of said ridges; characterized in that the holes (36) , in one of said rows, formed in the sides of the central ridge of said segment (5', 5") are located at said second distance from the end edge of said end portion (47) ; the other holes (36) in said row being located along a vertical line (L) between and substantially equidistant with respect to a vertical line through said holes (36) in the central ridge, and a vertical line through the centers of said slots (37) . 15) A semirigid, position-correctable, collision- energy-dissipating guardrail comprising a number of posts (3) , and at least one shaped rail (5) connected to each of said posts (3) by a respective fastening assembly (6) comprising an energy dissipator (21) located between said rail (5) and a spacer (13, 63) carried by said post (3); said spacer (13, 63) being connected to said post (3) by a group of cam guides (27,28; 67,68) cooperating with a group of engaging elements (29, 30) ; said group of cam guides (27,28; 67,68) being such as to provide for a substantially rigid connection at an initial stage in the collision of a vehicle, and for a position correction of said rail (5) at a subsequent stage in said collision; said cam guides being defined by cam slots (27,28; 67,68) on said spacer (13, 63); said engaging elements being defined by pins (29, 30) carried by said posts (3) and engaging a body (41) connected telescopically to a top portion (10) of said post (3) ; said body (41) permitting release of said rail (5) from said post (3) at a final stage in said collision; characterized in that said pins (29, 30) each engage a corresponding opening (11, 12) in said body (41) ; each of said openings (11, 12) being defined by a partition (49, 14) which is sheared by the corresponding pin (29, 30) at said final stage. 16) A guardrail as claimed in Claim 15, characterized in that said pins (29, 30) are of equal diameter; one of said partitions (49, 14) being located between said two openings (11, 12) .

17) A guardrail as claimed in Claim 15 or 16, wherein each of said posts (3) has a double spacer (63) connected by two dissipators (21) to two opposite shaped rails (5) ; said cam slots (67, 68) for said two rails (5) each having two arms symmetrical with respect to a vertical line; characterized in that at least one of said pins (29, 30) is carried by a plate (71) for preventing one of said pins (29, 30) from jamming erroneously in one of said arms .

18) A guardrail as claimed in Claim 17, characterized in that said pins (29, 30) are connected by a pair of plates (41a) , each located between a lateral plate (16) of the spacer (13, 63) and a wall (8, 8') of said post (3) .

19) A guardrail as claimed in one of Claims 15 to 18, wherein each of said posts (3) is defined by a metal channel section having an intermediate wall (8) located between two lateral walls (7) , each ending with a partial wall (8') parallel to said intermediate wall (8); said post comprising a portion (9) which is embedded into the road; characterized in that said portion (9) is reinforced by at least one metal brace (60) welded to said partial walls (8') .

20) A guardrail as claimed in claim 19, characterized in that said portion (9) is reinforced by a pair of said braces (60) welded, a given distance apart and at given depths, to the inside of said partial walls (8') .

21) A semirigid, position-correctable, collision- energy-dissipating guardrail comprising a number of posts

(3) , and at least one shaped rail (5) for withstanding collision by a vehicle; said shaped rail (5) being connected to each of said posts (3) by a respective fastening assembly (6) ; each of said posts (3) also being connected to a spacer element (51, 51') fitted with a wheel rail (50) extending parallel to and beneath said shaped rail (5) ; characterized in that said spacer element (51, 51') comprises a longitudinal opening (56) of constant width and engaging a pair of bolts (57, 57") fitted to said post (3) so as to slide along said opening (56) in the event of collision by vehicle wheels.

22) A guardrail as claimed in Claim 21, characterized in that said bolts (57, 57') are each inserted inside a vertical slot (58) on said post (3) ; each bolt (57, 57') being fixed by a nut in said opening (56) and in one of said vertical slots (58) so as to position said opening (56) horizontally.

23) A guardrail as claimed in Claim 22, characterized in that said bolts (57, 57') are of different diameters, so as to slide along said opening (56) in the event of impact by a car wheel, and so that the smaller-diameter bolt (57) is sheared to permit a certain amount of downward rotation of said wheel rail (50) in the event of impact by a heavy-vehicle wheel.

24) A guardrail as claimed in one of Claims 21 to 23, characterized in that said wheel rail is defined by a flat bar (50); said spacer element (51, 51') being defined by a sheet metal plate (52) having a bent tab

(53) to which said flat bar (50) is fitted; and said sheet metal plate (52) comprising a U-bent portion having an intermediate wall (55) in which said opening (56) is formed.

25) A semirigid, position-correctable, collision- energy-dissipating guardrail comprising a number of posts

(3) , and at least one shaped rail (5) connected to each of said posts (3) by a respective fastening assembly (6) comprising an energy dissipator (21) located between said rail (5) and a spacer (13, 63) carried by said post (3) ; each spacer (13, 63) comprising two opposite vertical edges (19,46; 64,64); characterized in that one edge (19, 64) of the spacer (13, 63) of a first of said posts (3) and the opposite edge (46, 64) of the spacers (13, 63) of the adjacent posts (3) are connected by a diagonal reinforcing member (72) .

26) A guardrail as claimed in claim 25, characterized in that each spacer (13, 63) has only one edge (64) connected to said diagonal reinforcing member (72) , which therefore assumes a zig-zag configuration. 27) A guardrail as claimed in Claim 26, characterized in that said diagonal reinforcing member is defined by segments, each defined by a flat bar (72) having two ends (74) bent at an angle for fitment to said edge (19,46; 64,64) .

28) A guardrail as claimed in Claim 27, characterized in that said flat bar (72) comprises an opening (73) of a length ranging from a quarter to a third of the length of said bar (72) to exploit the plasticity of said diagonal reinforcing member (72) along the whole length of the diagonal reinforcing member.

29) A guardrail as claimed in claims 13 and 28, characterized in that said dissipator (21) is defined by a sheet metal plate (23) bent into a U and having two lateral walls (24) connected to said spacer (13, 63), and an intermediate wall (25) connected to said rail (5) ; said sheet metal plate (23) having a horizontal opening

(26) extending at least the whole length of said intermediate wall (25) ; and at least one of the bent ends (74) of said flat bar (72) being housed in said horizontal opening (26) .

30) A guardrail as claimed in Claim 29, wherein each post (3) has a double spacer (63) connected by two identical dissipators (21) to two opposite shaped rails (5) ; characterized in that said bent ends (74) of one of said flat bars (72) are housed in the horizontal openings (26) of the dissipators (21) of two adjacent posts (3) .