User's Guide

Chapter 2: Pre-Installation Considerations
RTMS Echo User Guide ©2019 Image Sensing Systems Inc. 2-9
Placement in Side-Fired Highway Configuration
RTMS Echo is designed to mount on existing poles and road structures.
Figure 2-9
shows typical cases of RTMS Echo side-fired/highway sites. The
design considerations for each case are:
• Case 1 — Maximal utilization of the RTMS Echo zone capability.
Limitations are as follows:
– A 12-zone coverage may require a larger setback (the distance to
the first lane) mounting height and/or greater tilt setting (see
“Height, Setback, Tilt Requirements” on page 2-11
).
– In almost all cases, the RTMS Echo can resolve the barrier return
signal from that of the vehicles in the lane immediately behind it as
long as 50% of vehicle can be seen (see “Guardrails and Barriers”
on page 2-12).
• Case 2 — Overpass installations: Do not mount the RTMS Echo on a
perpendicular overpass. Instead, use poles located at least 5 m (17 ft)
from the overpass to avoid multi-path. Multi-path is a situation in which
the reflected signals from vehicles can also reach the RTMS Echo by a
secondary reflection from a large flat surface (such as a sign or
overpass).
• Case 3 — Using median poles to mount two RTMS Echo sensors, one
per direction may save poles but the designer should verify available
set-back (see “Height, Setback, Tilt Requirements” on page 2-11
).
• Case 4 — Sign-structure installations (see “Installing RTMS Echo on
Sign Structures” on page 2-14).
• Case 5 — Typical ramp metering site.