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c)
In the case of multi-lane links where more than one loop is provided,
the gap between two adjacent detectors on a link should be
approximately 2.5 m (based on the width of an average vehicle) so as
to balance under-counting and over-counting errors.
d)
Where carriageway width is restricted, the minimum 1m wide loop may
still be clipped by oncoming traffic. Where this problem is expected
unidirectional loops should be considered.
e)
The dimensions of the UD loop overlay are illustrated in Figure 6.
These SCOOT loop configurations can be used with Microsense,
Plessey ST, and Sarasota detector units.
Figure 7 illustrates a N+1 count loop configuration where N is the number of
traffic lanes. The length of count loops, in the direction of travel is fixed at 1.8
m. The width of loops and their spacing 'B' are dependent on site conditions,
these dimensions being shown on the appropriate site drawings. The distance
of the nearside loop to the kerb also varies with site conditions and should be
detailed on the site drawing.
The dimensions of the UD loop overlay are illustrated in Figure 7.
2.3.8 Turning Loops and SDE/SA Loops
Figure 8 to Figure 10 illustrate configurations for turning loops, and SDE/SA
loops. The turning loop Figure 9 can be connected to Siemens/Plessey,
Microsense and Sarasota detectors observing the calculation for loop turns
listed in section 2.5 of this document.
The rectangular loop SDE/SA configuration, Figure 8 is for connection to
Siemens/Plessey, Microsense or Sarasota detector units.
The chevron loop SDE/SA configuration Figure 10 should be used with
Sarasota MTS and Microsense MXE series detectors. This improves speed
measurement accuracy for motorcycles.
NOTE: Siemens controllers and Pelicans for new installations will be
configured for 3.66 metre speed measuring base in line with current GEC and
Microsense controllers. Earlier Plessey controllers may have been configured
for 3.05 metre speed measuring base and other manufacturers' earlier
controllers for various different bases. When re-cutting an existing loop check
with the existing controller for the correct loop spacing.
With intersection controllers the configuration must be checked to verify the
loop spacing.
With T110 Pelicans Address 217 should be greater than 0 for 3.66 metre
speed measuring base.
2.3.9 MOVA Loops
Figure 11 and Figure 12 illustrate MOVA loops; it is recommended that
diamond loops should be used where lane width allows, with a minimum size
of 1 sq m and 1.6 m to 1.7 m in the direction of travel. Where lane width is
restricted, other loop configurations may be used. For example, where MOVA
667/HE/20663/000
Issue 13
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