1. SCATS Adaptive Traffic System
TRB Adaptive Traffic Control Workshop
January 2000
Session 2 - Equipment Requirements
For further information contact:
Neil R. Gross

2. SCATS Architecture SCATS is arranged as a distributed system.
The top level of computers, the Central Management System, provides database and management function support. This level collects and provides access to system data and fault information, supports the maintenance management subsystem and maintains the travel time database if implemented.
The Regional Computers each connect up to 250 intersections and provide the strategic, that is area, traffic control function. This is where the adaptive algorithm executes. The Regional Computer can also provide some facilities that would normally reside in the CMS such as data collection, event (fault) logs and route preemption facilities for systems that are implemented without a CMS.
At the bottom level are the intersection controllers which provide the tactical signal control and the important data collection and processing function for the adaptive algorithm.

3. SCATS System Architecture Minimal System - Single Region
Looking at the SCATS configuration in a more equipment oriented way this slide shows the basic SCATS system. This comprises a single Regional Computer with up to 250 intersection controllers attached.
The latter can be either point-to-point or multidrop connected. Facilities also exist for TCP/IP connection when a suitable controller is available.
Up to 15 workstations may be connected via LAN, dedicated line or dial-in.
Note that the SCATS Regional Computer also supports dial-out and dial-in intersection controller connection. This is used to connect to marginal area intersections for data change or alarm collection.

4. SCATS System Architecture SCATS 1 - with Integration Server
This slide shows a full SCATS implementation with three of the possible 32 Regional computers and an Interface Server.
The latter provides an integration interface for the connection of SCATS to other Transportation Systems. This was first implemented for integration of SCATS with the Road Commission for Oakland County’s Transportation Information Management System (TIMS).
As shown Regional Computers can either be LAN or dedicated line connected.
Also shown on this slide are ramp metering controllers – the SCATS Regional computer includes an adaptive ramp metering facility. This is installed in Minneapolis.
All computers are PCs with the exception of the Central Management Computer which is a DEC VAX or Alpha. Note that only 128 intersections per Regional Computer are shown. This is a current limitation of the VAX based CMS.
There is a extensive ongoing development program for SCATS which will replace the VAX as shown on the next slide.

5. Configuration - SCATS2
SCATS 2 will have a Management layer comprising networked PCs. New communication facilities and other features will be available. A CORBA based approach for distributed network processing is being considered.

6. SCATS Sensors
Controller collects number of spaces and total space time during green of each movement, each cycle for use by SCATS adaptive algorithm.
Actual movement data collected by stop line detectors allows accurate split determination.
SCATS requires information about each controlled traffic movement for the adaptive algorithm.
This information includes the total space time and the number of spaces for each lane movement.
It gathers this data from presence sensors.

7. SCATS Sensors
Loop Detectors or equivalent (video detection in Oakland County MI) in most lanes at the stop line.
Some lanes can be left without detectors.
Most commonly the sensors are loop detectors with a 6 x 15 foot format placed near the stop line. Video detection has also been used successfully in the RCOC FastTrac system.
Detectors are placed in most lanes. About 60 to 70% detectorization can be typically expected.
Each controlled movement requires at least one detector. Where there are multiple lanes for a movement some lane detectors can be omitted after consideration of redundancy requirements and lane usage.
Also main street detectors at subsystem minor intersections can be omitted as the main street splits and minor intersection cycle length are determined by the subsystem critical intersection or the time-of-day fallback system- Flexilink.

8. Communications - SCATS1
This slide shows the Communications facilities used in the current SCATS implementation .
Communications to the Regional computers is shown as LAN or Full Duplex data line.
Regional to Intersection communication is Bell 103 (300 bps) point-to-point or V22 multidrop. Both can be implemented on user-owned copper pairs (single pair) or leased lines. RS232 connection is also available for other transmission mediums e.g. fiber.
Operator workstations are typically LAN or RAS-PPP connected although direct or dial-up serial connection is also available

9. Communications - SCATS2
This slide shows the anticipated changes to communications that will be available with SCATS 2
NTCIP Center-to-Center communications will be provided for ITS integration while field devices will be connected to the SCATS intersection controller using NTCIP Class B protocol.
The biggest changes will come for Regional-to-Intersection Controller communications where V34 (using TCP/IP via RAS PPP) may provide a higher speed link with routable protocol. Also being examined is an NTCIP Standard Global Objects implementation with special MIB.
Alternative communications options are already available at the Regional Computer end with the PC/NT implementation of SCATS. Realization, however, will require release of new controllers that support the alternative communication methods.

10. SCATS Traffic Controllers -Existing
170
NEMA
AWA Delta 170 upgrades existing 170 controller to support SCATS.
Relay Module added for sense/control of cabinet status.
AWA Delta 3N controller replaces existing NEMA controller.
Connections are via existing A, B and C connectors.
One back-panel link required.
The existing controllers provide for implementation in both NEMA and 170 environments.
The SCATS 170 adapter upgrades an existing 170 timer to SCATS functionality. Minor additions to the 170 cabinet are required.
The Delta 3N controller replaces a standard NEMA controller and is compatible with the NEMA cabinet.

11. SCATS Traffic Controllers -Planned
SCATS 2070N
New controllers include models based on the Advanced Transportation Controller (ATC or 2070) specification. This will provide implementations suitable for both NEMA (using the 2070N) and 170 (using the 2070) as well as the new ATC cabinet.
Development is progressing on these implementations.

12. SCATS Hardware Requirements
Management Computer - Database and Mgt Systems
SCATS 1 DEC VAX/ALPHA, OpenVMS
SCATS 2 Networked PCs
Regional Computer - Strategic Control
Personal Computer with Windows NT
Digi Serial Interface system.
Hardware requirements include:
CMS
SCATS 1 VAX or Alpha computer with OpenVMS Operating System.
SCATS 2 Networked PCs with Windows NT Operating System
Regional Computers are PCs running Windows NT Operating System. The Digi C/X serial interface system is used to provide up to 250 intersection ports.

13. SCATS Hardware Requirements
Operator Workstations - Up to 15
Personal Computer with Windows NT or Windows 98
SCATS Controllers - Tactical Control
up to 250 per Regional Computer

14. SCATS Installation Cost Ranges 64 Intersection System
Central Hardware approx. $ 30,000 (small VAX)
Central Software approx. $40K to $70K
Regional Hardware approx $20K
Regional Software approx $70K

15. SCATS Installation Cost Ranges 64 Intersection System
Local Controllers approx. $3.5K to 5.5K, total say $300K
Communication Network - Included above
Detection Sensors …. Standard loop amplifiers and 6 x 15 loops…..$230K?
Total - approx $650K for single Regional (No CMS)
Detection Sensors ……..standard loop detector amplifiers and 6 x 15 loops say $230K Depends on final number of detectors required and loop cutting cost

16. SCATS Operations & Maintenance Cost Ranges - 64 Intersection System
Central Hardware approx $3K per annum
Central Software approx $4K per annum
Regional Hardware - negligible.
Regional Software approx $8Kpa
Regional Setup & Support - similar to current support level plus quarter to half man year per annum.

17. SCATS Operations & Maintenance Cost Ranges - 64 Intersection System
Local Controllers - similar to current controllers
Communication Network - User owned TWP? or VG Leased Line approx $22/month
Detection Sensors …loop maintenance? Depends on quality of original installation and road surface...
Detection Sensors ……..loop repair? Depends on quality of installation and roadway……

18. End
Thank You