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The VMS’s are programmable traffic control devices that display messages composed of letters, symbols or both. They are used to provide information about changing conditions in order to improve operations, reduce accidents, and inform travellers. VMS’s are to provide the following information:
• recurring congestion,
• non-recurrent congestion,
• weather-related problems,
• congestion due to special events,
• routes,
• speed restrictions, and
• other changing conditions or requirements.
The information displayed on VMS’s can be classified as advice, warnings, guidance and other requirements.
1.2 Functional Requirements
The following functional requirements are specified.
1.2.1 Warning and Advisory
VMS to warn drivers of traffic problems such as the existence of a downstream incident, work zones, or hazardous road conditions, and provide some advice for the drivers.
1.2.2 Guidance
the guidance objectives for the VMS, i.e. to directly provide drivers with instructions on route selection, lane changes, diversions, etc. Advisory for a Future Event. The advisory message for a future event, such as a lane to be closed, can help drivers divert to alternative routes, or make decisions by themselves.
1.3 Self diagnosis
The VMS shall have self-test diagnostics features to test the VMS for correct operation. In the event of any problems, this shall be reported to the Central Control Computer.
1.3.1 Sign Technologies
The various technologies are available and the selected option for this design submission will be Electronic – LED. The specifications dictate that the image pixels shall be made up using a cluster of solid-state diodes mounted in a socket.
1.3.2 Display
The display background shall be non-reflective and the display shall be U.V. resistant. There are 3 types of displays:
• Text only display, and these shall be displayed in two contrasting colours at Present
• Graphics only display
• This display must be able to produce colours and shapes according to the standard road traffic requirements
Combination display, i.e. which combines the text only and graphics only units into one unit. .
1.3.3 Languages
the system must be bilingual, able to display English and another language such as Hindi ( DEVNAGRI) can be designed for any language supported by windows standard FONT on specific requirements .
1.3.4 Sign Data Storage
VMS’s shall be able to store all the required data for displaying information locally can be triggered on receiving the command.
1.4 Central Control Computer
A central control computer ( can use existing or new Control room ), or MIU to programme the individual VMS’s. The central control computer shall be capable of setting an individual VMS, or group of VMS’s, to display either one of the pre-set messages, or symbols, or a text message, or symbol, entered into the computer via the control computer keyboard, or by another means. In addition, the central control computer system shall be capable of being programmed to display an individual message on a VMS, or group of VMS’s, at a pre-set date and time
• The central control computer Can also store, in a suitable database, information about the messages displayed on each VMS. The minimum information to be stored
The central control computer Can on a regular (pre-set) basis test each individual VMS. This test should be exhaustive and determine if the system is fully operational.
1.5 Communication
The communication method : Communications Backbone System Design submitted under separate cover.
Gsm Based
Fibre optic
Ethernet
Pstn Line modems
1.6 Location of Equipment
The location of the equipment shall be strategically placed
• Ensure maximum visibility for the road user from all the traffic lanes of the carriageway,
• Allow the road user sufficient time to read and comprehend the message and react.
Equipment shall either:
• Be placed off-shoulder and clear of the traffic and any emergency lane, or
• On overhead gantries.
Positions shall be determined so that extraneous effects such as direct sunlight are negated.
Design Process
1.7 Design parameters
Variable Message Sign (VMS) Systems applied in a highway environment has the purpose of conveying important information to the motorists. The system can be used to display warnings, traffic advice, route guidance and emergency messages to motorist from a Central Control Room (CCR). Proper placement and utilisation should result in a safer and less intrusive journey for the motorist.
The VMS system network is made up of number of VMS’s placed at strategic locations along the motorway. The VMS’s communicate with a control computer located at the CCR. The data communication between the VMS and the CCR computer is achieved using the Communication desired by client along the Highway. The VMS is provided with a RS485 serial interface & RS 232 as per requirements ,
The VMS can display text and graphic messages using a Light Emitting Diode (LED) display. A number of LED’s are combined to form a display pixel. The pixels are used to form alphanumeric characters or graphic pattern to be displayed.
The VMS is custom built item can provide number of lines & character height to clients requirements ( Maximum size of Display available is 2 mtrs X 4 mtrs)
The message to be displayed can be stored in the local non-volatile memory resident on the VMS or can be communicated to the VMS from the CCR computer via the network.
The messages can be displayed according to a pre-defined schedule or on a query basis.
The CCR operator is provided with a Graphical User Interface (GUI) front-end application. There is a database storing all data, messages, and VMS status information related to all VMS’s in the system.
The VMS can display three lines of Hindi or English character. Hindi character display is based on 16x10-pixel format while English character display is based on 5x7pixel format.
In the event that a text / graphic message is displayed, the number of characters (Hindi/ English) per line will reduce to accommodate the graphics.
1.8 System Physical Architecture
See Figure - General Layout of VMS for the general layout which serves as the physical architecture.
1.9 Environmental factors
Ambient operating conditions:
• Temperature - 0° C to 50 °C
• Relative humidity – up to 95% RHS
• Storage Conditions:
• Temperature - 0° C to 70 °C
• Relative humidity – up to 95% RHS
• Ingress Protection:
• IP65 for VMS Display modules.
1.10 Maintenance Accessibility
The VMS is designed with a modular approach. As described above, the system consists of multiple display modules, where each module can be removed and replaced individually without affecting others.
Access to each sign is dependent on the surrounding conditions. Generally, a permanent working platform with restricted access will be utilised.
1.11 Motorist Visibility
The VMS provides an alphanumeric or graphical pattern display to the motorist, visible from a distance of approximately 300 metres. Messages can be displayed in the form of an alphanumeric sequence, consisting of lines of Hindi or English characters and / or graphics as per customer choice
1.12 Security
The VMS system is designed to send an alarm to the CCR operator in the event of unauthorized access. The VMS cabinet is designed to prevent easy access to vandalism. CCTV or VIDS shall be used to monitor the VMS signs where possible.
1.13 System Audit Requirements
The VMS control system is able to report on all the activities related to the VMS display controlled by it. The report can be generated on the following categories:
• Messages displayed by a particular VMS within a specified period
• Messages displayed by a particular VMS on a type basis within a specified period
• Messages displayed by a particular VMS on a per shift basis
• Schedule of messages to be displayed
• Status report of all VMS displays in the system for a specified period
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