Walnut Creek, California, United States
Concord, California, United States
Summary Information
The Cities of Concord and Walnut Creek, California investigated alternatives for transmitting real-time traffic video from field devices to each city’s respective transportation operations center (TOC). During the design phase of the project, each city conducted a budgetary cost comparison to examine the capital costs associated with two alternatives:
(1) upgrading the existing network of copper wire (twisted pair) traffic signal control communications network
(2) converting to fiber optics.
Both alternatives would provide enough bandwidth for high-quality video; however, the fiber option would allow for future communications needs (i.e., internal network, DMS, etc). Although the copper wire option would have limited functionality, it would be less expensive, and enable the city to upgrade other signal system elements such as traffic signal controllers.
The table below shows the results of the pre-construction cost comparison (based on 1-mile of transmission distance).
Existing Copper
Network |
New Fiber
Network |
|
---|---|---|
Remove Existing Cable |
$10,560
|
|
Furnish and Install FO Cable |
$26,400
|
|
Fiber Video Transceivers |
$5,000
|
|
Video Transceivers for Copper |
$10,000
|
|
Interconnect Cable Modifications |
$1,000
|
Once the decision was made to use the existing copper infrastructure, the twisted pairs within each interconnected cable were reallocated to provide full duplex (two-way) communications between CCTV cameras and the TOC.
Both cities intended to install a combination of fixed and “dome” style CCTV cameras on existing poles and route video and camera data cables back to the traffic signal controller cabinet at each intersection. Inside the cabinet, the video cable (coaxial cable) from the camera was connected to a video transceiver and the camera control cable (two-conductor cable) was connected to an amplifier/repeater.
During the upgrade project, the City of Walnut Creek took the opportunity to repair and install additional interconnect cables to accommodate video throughout the city. They minimized the amount of transmission equipment needed by placing the equipment as far apart as possible without exceeding a 3,500 foot signal attenuation limit. In each control cabinet, video signals were transmitted onto twisted-pair interconnect cables and then re-amplified every mile (5 miles maximum depending on condition of cable) until the signal reached the head-end terminal block at the TOC. At the head-end, a receiver equipped with one video card per camera accepted the signal and transferred it to an analog video switch and video console where it could be viewed by TOC operators.
In Concord, the city opted to transmit the data digitally back to the TOC without the need for repeaters. This configuration required that protocol converters be installed at each controller cabinet, and at the TOC.
Cost estimates for each alternative were prepared from actual bids (see tables below). Only capital costs were considered. The cost of traffic control, controller upgrades, and mobilization were not included because theses costs were roughly equivalent between the two options. The two estimates assume a 5-mile corridor with cameras installed every mile beginning at the TOC.
Alternative 1: Video over existing Copper Interconnect
End of Line
|
Mile 1
|
Mile 2
|
Mile 3
|
Mile 4
|
Head End
|
Total Quantity
|
Unit
|
Unit Cost
|
Item Total
|
|
---|---|---|---|---|---|---|---|---|---|---|
Camera |
1
|
1
|
1
|
1
|
1
|
|
5
|
EA
|
$7,500
|
$37,500
|
RS-422 Repeater |
1
|
1
|
1
|
1
|
1
|
|
5
|
EA
|
$450
|
$2,250
|
1-Channel Video Transceiver |
1
|
|
|
|
|
|
1
|
EA
|
$3,250
|
$3,250
|
2-Channel Video Transceiver |
1
|
1
|
|
|
|
|
1
|
EA
|
$4,300
|
$4,300
|
Rack-Mount Chassis |
|
1
|
1
|
1
|
1
|
|
4
|
EA
|
$3,900
|
$15,600
|
1-Channel Rack-Mount Video Transceiver |
|
3
|
4
|
5
|
5
|
17
|
|
EA
|
$1,250
|
$21,250
|
Interconnect Terminations |
1
|
1
|
1
|
1
|
1
|
1
|
6
|
EA
|
$200
|
$1,200
|
Replace damaged Interconnect (assume 1 mi) |
|
|
|
|
|
1
|
1
|
MI
|
$10,560
|
$10,560
|
Option Total |
|
|
|
|
|
|
|
|
|
$95,910
|
Alternative 2: Video over new Fiber Optic Cable
End of Line
|
Mile 1
|
Mile 2
|
Mile 3
|
Mile 4
|
Head End
|
Total Quantity
|
Unit
|
Unit Cost
|
Item Total
|
|
---|---|---|---|---|---|---|---|---|---|---|
Camera |
1
|
1
|
1
|
1
|
1
|
|
5
|
EA
|
$7,500
|
$37,500
|
Video + Data Fiber Transceiver |
1
|
1
|
1
|
1
|
1
|
|
5
|
EA
|
$3,200
|
$16,000
|
Video + Data Fiber Receiver |
|
|
|
|
|
5
|
5
|
EA
|
$3,100
|
$15,500
|
Furnish & Install 12-Strand Fiber Optic Cable |
1
|
1
|
1
|
1
|
1
|
|
5
|
MI
|
$15,840
|
$79,200
|
Make & Test Fiber Optic Splice |
2
|
2
|
2
|
2
|
2
|
10
|
20
|
EA
|
$175
|
$3,500
|
Fiber Optic Splice Closure |
1
|
1
|
1
|
1
|
1
|
5
|
$1,100
|
$5,500
|
||
Fiber Optic Cable Termination Unit |
1
|
1
|
1
|
1
|
1
|
5
|
$500
|
$2,500
|
||
Fiber Optic Patch Cords |
1
|
1
|
1
|
1
|
1
|
5
|
10
|
$100
|
$1,000
|
|
Option Total |
$160,700
|
Real-Time Video over Copper Networks: A Tale of Two Cities
Video over existing copper interconnect: Capital Cost $95,910 for a 5 mile corridor.
Video over new fiber optic cable: Capital Cost $160,700 for a 5 mile corridor.