GB2417817A

GB2417817A - Traffic signal, in particular pedestrian crossing, with restricted viewing angle.

Info

Publication number: GB2417817A
Application number: GB0517964A
Authority: GB
Inventors: Peter Michael Hutchinson; Andrew Richard Bell
Original assignee: AGD Systems Ltd
Current assignee: AGD Systems Ltd
Priority date: 2004-09-04
Filing date: 2005-09-05
Publication date: 2006-03-08
Anticipated expiration: 2025-09-05
Also published as: GB0419713D0; GB2417817B; GB0517964D0

Abstract

A traffic signal includes a viewing angle control screen (24, Fig. 3) for restricting the viewing angle of the traffic signal display to a selected angular range. In particular the traffic signal is a pedestrian crossing signal comprising a pictogram screen having a red stationary man 16 and a green walking man 18 illuminated by LEDs (22, Fig. 3). The viewing angle control screen may comprise a microlens film, a microlouvre screen, comprising a plurality of louver elements, or a microprism structure. Also disclosed is a traffic signal housing (10, Fig. 7) which allows for azimuthal adjustment of the display relative to the traffic pole to which it is attached.

Description

Traffic Sionals This invention relates to a traffic signal and traffic

signal housing and in particular, but not exclusively, to pedestrian traffic signals for use at pedestrian crossings such as for example Puffin, Pelican and Toucan crossings.

In a Pelican crossing, the display indicating whether to walk or stop is located on the far side of the pedestrian crossing (a "far side display") and road safety studies have shown that pedestrians tend to ignore the far side display and rely instead on observing the traffic and walking when it is clear or the traffic has stopped. In the Puffin crossing the display is located on the near side of the pedestrian crossing (a "near side display"), on the primary pole, that is the upstream pole relative to the nearside traffic so that the user is facing the oncoming traffic when looking at the nearside display. The Puffin crossing also includes additional sensors and controls to optimise pedestrian and motor traffic flow.

Conventionally, the displays have been designed to incorporate complex refractive surfaces to generate a distribution of light visible over a wide viewing angle so that the display is visible from a wide range of angles, typically with a Gaussian distribution. We have found that a problem can arise around busy intersections where there may be several nearside displays which may be visible to a pedestrian and the pedestrian may look at the wrong display for a particular crossing, with potentially fatal consequences.

Accordingly, we have identified a need for a traffic signal in which the field of view is narrower than conventional displays, to address this problem.

Furthermore by reducing the field of view of the display pedestrian users may be encouraged to stand in a selected safety region relative to the crossing in which they face the direction of the oncoming traffic.

In conventional traffic signals it is known to restrict the field of view by fitting extended cowls to traffic lights or to fit external louvers, but these external mechanical fittings are not suitable for displays which are easily accessible at ground level.

In one aspect, this invention provides a traffic signal including a light source, the traffic signal being operable selectively to display at least one visual signal to a viewer, said traffic signal further including a viewing angle control screen for restricting the viewing angle of said display to a selected angular range.

The advantage of this arrangement is that the use of a screen means that the viewing angle control screen can be located within the traffic signal control housing thereby allowing a compact arrangement, and making it 1 5 vandal-resistant.

The light source may typically comprise first and second arrays of light emitting elements, for example first and second arrays of LEDs, the first and second arrays being independently operable to display a respective visual image.

The traffic signal may typically include a pictogram screen for being illuminated by the light source and containing two different images. For example, in a pedestrian traffic signal the images may comprise the red stationary man and the green walking man.

The traffic signal may include a microlens film disposed between the light source and the pictogram screen to diffuse/distribute the light from the light source.

The viewing angle control screen may be in the form of a microlouvre screen comprising a plurality of louvre elements disposed such as to restrict the viewing angle relative to said screen.

The use of microlouvres creates a distribution which attenuates more rapidly with angle compared to existing arrangements and which restricts the viewing angle of the signal off-axis in the azimuthal plane.

In one arrangement, the luminous intensity is controlled in this manner to be less than 5% at the desired angle which may be for example 30 from the central axis.

Depending on the particular application, the traffic signal may be configured so that the included viewing angle is symmetric to a central frontal axis of the display, or it may be offset.

Although the viewing angle control screen could be disposed on the other side of the pictogram screen from the light source it is preferred for it to be located on the side of the pictogram screen facing the light source. The pictogram screen can typically be formed of a tough plastics material such as polycarbonate and thus be vandal-resistant.

The traffic signal preferably comprises a housing containing the light source viewing angle control screen and other components.

Conventionally, due to the wide viewing angle, there has been no need to provide angular adjustment for the nearside traffic display. In practice, the display housing has had two fixing holes and the fitters have simply marked up the appropriate location on the post and drilled two holes to align with those in the back of the housing, and then threaded through a thread U-bolt and applied two nuts to secure the housing to the pole. However, this requires considerable precision when fixing the display to the traffic pole, and even more so when the viewing angle is narrowed, and there is a need to control the area from which the signal can be viewed.

Thus, in a preferred aspect, the housing includes an arrangement designed to allow azimuthal adjustment of the housing relative to the traffic pole to which it is attached in use, to adjust the orientation of the viewing 1 0 angle.

The attachment arrangement may comprise a pair of parallel slots in the region of the housing which contacts the traffic pole in use. Preferably, said slots are arranged so as to accommodate different attachment means, such as different sizes of U-bolts, and/or to align with apertures in the traffic pole, such as cable apertures. Even more preferably, the size of the slots may be varied to allow some play in the alignment of the housing with the traffic pole.

The advantage of this arrangement is that the display can be adjusted on the traffic pole before it is securely attached, thereby ensuring that the viewing angle is correctly positioned for pedestrians to see. In addition, it is

easier to erect than prior art arrangements.

The invention also extends to an assembly comprising a traffic signal as described above in combination with a traffic pole.

Whilst the invention has been described above, it extends to any r inventive combination of the features set out above or in the following

description.

The invention may be performed in various ways, and by way of example only, an embodiment thereof will now be described in detail, reference being made to the accompanying drawings in which: Figure 1 is a general perspective view of a pedestrian nearside signal in accordance with this invention; Figure 2 is a schematic side view showing a prior art optical arrangement for a traffic signal; u Figure 3 is a schematic side view of an optical arrangement in accordance with this invention; Figures 4(a), (b) and (c) are schematic views respecuvey or line wue viewing angle of the prior art optical arrangement of Figure 2, and symmetric and offset narrow viewing angles of embodiments of the invention of the type shown in Figure 3; Figure 5 is a schematic view of the rear part of a traffic signal housing in accordance with this invention secured to a traffic pole and having an azimuthal adjustment facility, and Figure 6 is a top plan view of the arrangement of Figure 5.

an Figure 7 is a schematic view of the rear part of a traffic signal housing in accordance with another aspect of this invention, secured to a traffic pole and having an azimuthal adjustment facility.

Figure 8 is a top plan view of the arrangement o ryue I. Figure 9 is a schematic view of the hole and bolt arrangement in Figures 7 and 8.

Referring to Figures 1 and 2, a pedestrian nearside signal comprises a rear housing 10 and a hinged cover 12 which supports a polycarbonate pictogram screen 14. The polycarbonate pictogram screen has formed thereon two distinct cut-out images of the stationary (red) man 16 and the walking (green) man 18. Each man is illuminated as and when required by respective arrays of red and green LEDs arrays within the housing, as described below.

As seen in Figure 2, in a conventional arrangement a microlens diffuser film 20 is disposed behind the polycarbonate pictogram screen 14 and is illuminated by the LEDs of an LED PCB assembly 22. This arrangement gives a wide viewing angle as seen in Figure 4(a).

In the embodiment of this invention, shown in Figure 3, a viewing angle control screen 24, here in the form of a microlouvre screen, is located between the pictogram screen 14 and the microlens film 20 which, as before, is illuminated when required by the LED PCB assembly. The microlouvre film is oriented such that, in azimuth, the viewing angle is considerably restricted as compared to that of the arrangement of Figure 2. Examples of the narrow range of view are given in Figures 4(b) and 4(c) from which it can be noted that the viewing angle may be symmetric or offset as a particular application requires.

The viewing control screen may be of any suitable relatively thin sheet material which restricts the viewing angle. Accordingly, it may comprise a microlouvre or a microprism structure such as is contained in the material marketed under the trade name "VIKUITI" by 3M or more generally in Light Control Film products marketed under the designation LCF series.

An advantage of a microlouvre construction where the depth is less than, say, 2mm is that the signal output quality is not readily compromised from that of a Gaussian generated distribution. This means that the signal aspect is free from excessively dim or bright areas and continues to have a high uniformity. Also, the internal microlouvre style construction is not readily discernable by the viewer as the signal is typically mounted where a push button would be and the viewer is close compared to traditional traffic signals.

This is because given the low depth of the microlouvres such individual microlouvre are very thin and at a small separation from each other. These items contribute to preserving the pictogram integrity of the signal.

Referring now to Figures 5 and 6, the rear housing part 10 is provided with two parallel slots 26 through which project the free ends of a Ubolt 28 which has been threaded through a pair of vertically aligned holes (not shown) in the traffic pole 30. A curved plate 32 fits over the free ends of the bolt 28 with the assembly being clamped by two nuts 34. The plate 32 has a cable aperture 36 which aligns with a similar aperture (not shown) in the cable pole, and the rear of the housing includes a slot 38. In this manner, the housing may be adjusted in azimuth by +/-25 or so to allow the viewing angle to be oriented as required.

In an alternative embodiment, shown in Figures 7 and 8, the rear housing part 10 is provided with a plurality of fixing slots 26, and the free ends of a U-bolt, as described above, can be seen projecting through slots 26a. In this example no plate is present, and the free ends of the U-bolt are therefore clamped by two nuts 34 directly to the rear housing part. This clamping arrangement is shown in more detail in Figure 9, where it can be seen that a washer 39 is placed over the free end of the U-bolt, against the slot, and the nut 40 then threads on to the bolt end 41.

Slots 27 and 38 are provided so that they align with cable apertures 37 and 36, respectively.

In this manner, the housing may be fitted and adjusted in azimuth by + 15 or so, as shown in Figure 9, to allow the viewing angle to be orientated as 1 0 required.

Although Figure 7 shows a housing having five slots, it will be appreciated that the number and placement of the slots may be designed so as to accommodate different sizes of U-bolts and cable apertures, or to allow the housing to be fitted higher or lower on the traffic pole, provided this does not effect the structural integrity of the housing. Thus, the housing may be adapted to fit to all types of traffic poles, and placed at an appropriate height according to each situation.

In addition, the size of the slots may be varied to accommodate for U bolts of different thicknesses, or to allow some play in the alignment of the free ends of the U-bolt with the nuts, thereby making it easier to affix the housing to the traffic pole.

Claims

1. A traffic signal including a light source, the traffic signal being operable selectively to display at least one visual signal to a viewer, said traffic signal further including a viewing angle control screen for restricting the viewing angle of said display to a selected angular range.

2. A traffic signal according to claim 1, wherein the light source comprises first and second arrays of light emitting elements that are independently operable to display a respective visual image.

3. A traffic signal according to claim 2, wherein the light emitting elements are LED's.

4. A traffic signal according to any preceding claim, wherein a traffic signal further includes a pictogram screen for being illuminated by the light source and containing two different images.

5. A traffic signal according to claim 4, wherein the images comprise a red stationary man and a green walking man.

6. A traffic signal according to any preceding claim, wherein traffic signal further includes a microlens film disposed between the light source and the pictogram screen.

7. A traffic signal according to any preceding claim, wherein the viewing angle control screen is in the form of a microlouvre screen comprising a plurality of louver elements disposed such as to restrict the viewing angle relative to said screen.

8. A traffic signal according to claim 7, wherein said microlouvre screen provides a half-angle optical profile in which the viewed intensity at a half angle of 30 is less than 5%.

9. A traffic signal according to any preceding claim, wherein the traffic signal is configured so that the included viewing angle is symmetric to a central frontal axis of the display.

10. A traffic signal according to any preceding claim, wherein the traffic signal is configured so that the included viewing angle is offset relative to a central frontal axis of the display.

11. A traffic signal according to any one of claims 4 to 10, wherein the viewing angle control screen is located on the side of the pictogram screen facing the light source.

12. A traffic signal according to any one of claims 4 to 11, wherein the pictogram screen is formed of a tough plastics material.

13. A traffic signal according to any preceding claim, which comprises a housing containing the light source viewing angle control screen and other components.

14. A traffic signal according to claim 13, including attachment means adapted in use to allow azimuthal adjustment of the housing relative to the traffic pole to which it is attached.

15. A traffic signal according to claim 14, wherein the arrangement comprises at least a pair of parallel slots in the region of the housing which contacts the traffic pole in use.

16. A traffic signal housing for attachment in use to a traffic pole, said housing including attachment means for cooperation in use with fixing means, said attachment means allowing azimuthal adjustment of said traffic signal housing relative to said pole.

17. A traffic signal housing as claimed in claim 16, wherein said attachment means comprises at least two generally parallel slots for receiving fixing means associated with said traffic pole.

18. A traffic signal substantially as herein described with reference to the accompanying Figures.

19. A traffic signal housing substantially as herein described with reference to the accompanying Figures.