Design Assignment Template for Increasing Bicycle Traffic

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Department of Electrical Engineering and Electronics
ELEC120/ELEC123
DESIGN ASSIGNMENT TEMPLATE
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Introduction
The City Council wishes to increase the number of people travelling by bicycle in the city. This has a number of
benefits, both for the health of individuals and will reduce wear on road surfaces, saving the City money in the
longer term.
A problem which has been highlighted concerns the responsiveness of sensors at traffic light controlled
junctions; currently these are not designed to detect cyclists.
The following report contains evaluation and recommendations for replacing the old system and replacing them
with a new, more cycle-friendly system.
Background
There are three types of detection system that are being considered as popular and effective method for
detecting cyclist at traffic junctions. The three methods are that is considered here are based on three different
technologies. Among three methods one is radar-based and the other is thermal-based while another one is
loop based detection system. Both of these technologies are discussed in details in this context.
Applications of redder at traffic junction are widely considered around the world for detecting any kind
of physical, not just some motor vehicle, but cyclist too. At intersections devices that are installed, it's known as
interceptors. This interceptor integrates rather and works on the principle of rather detection technique to
detect cyclists. This device this combines microwave and presence sensor, which helps in detecting a vehicle and
offer enough precision that is required and effective for determining whether a vehicle has to four or more who
this because it has the ability to detect the kind of vehicle that is about to cross the traffic (Fhwa.dot.gov 2019).
Hence, it helps in controlling signal time in accordance with that.
Another detection system that is considered for detecting cyclists at traffic sanctions is a based
detection system. In a thermal based detection system the system analyses thermal radiation from object. The
system considers heat that is radiated from the object. And then, according to that it then analyse the position
of the object, and hence, help in the data mining, the position of the object, which helps in detecting the object
(NC Bike Ed 2019). That is why this technology has the potential to be applied at traffic junctions to detect
vehicles and control traffic signals with accordance to that.
In loop based vehicle detection system inductor loop that helps to detect the presence of object analyse
measurement of change in an electric field. This technique has several benefits which are discussed in this
context. Some of the vector-based detection systems is that it has higher speed accuracy and provide route
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ELEC120/123 Design Assignment 2018-19

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accuracy counting traffic. Along with that, it provides excellent stability determination of vehicles how is the
most significant feature if this system is affected when there is a change in weather and traffic environment (NC
Bike Ed 2019).
Due to this properties induction based detection systems are an excellent choice for detecting objects and it is
also applicable in detecting the presence of vehicles in traffic junctions which is the topic of discussion in this
context.
The loop-based detection system works like a metal detector which analysing changes in electric field determine
of any object. Once any kind of vehicle moves forward through a loop sensor there is a change in a loop field
which implies presence object and hence the object is detected. Although the process is complex it is based on
this principle that is analysed in this context.
As an induction based loop detection system works on the principle of changes in the electric field, it is
important to note that not all materials are not equally detected in this process. Hence appropriate
consideration is required for selecting appropriate construction material for bicycles so that bicycles are easily
and effectively detected with this induction based detection system. The best choice for the material is either
aluminium or steel as these two materials are effectively detected by this detection system. However, it is
important to note that carbon frames are also detected in this system but the strength of the field has to be
very effective to effectively detect carbon frames. However, the best choice for construction materials is either
aluminium or steel.
Proposed designs
In the table 1 the magnetic fields in the loops are drawn and then the approximate magnetic field intensities are
sketched on the length of shape. The magnetic field intensity is given by,
H = Ampere-turns/meter.
Hence, the regions with large number of turns will have high magnetic field intensities and vice versa. Hence,
field intensities of the shapes are drawn accordingly in the Table 1. From the table it can be seen that the
magnetic field intensity is uniform only for a circular loop and for other shapes the intensities are not constant
through the length of the shapes. Now, when a bicycle (made of conductive material) enters into the magnetic
field of the shape the alternating current supplied to the magnetic field induces a weak electrical current. That
weak electrical current induces a magnetic field which work opposite to the original magnetic field by Lenz’s
law. This changes the resonant frequency of the sensor coil and this change is detected by circuit installed in the
traffic signal controller and thus indicate that a vehicle is present. Now, the optimum bicycle position such that
detection occurs properly within short amount of time is to place the bicycle in the maximum field intensity of
the loop. In case of circular shape the bicycle can be placed anywhere in the magnetic field but for other shapes
a cyclist need to position the bicycle in the maximum intensity zone for quick and precise detection of the
vehicle.
Comparison between rectangular and circular induction loops
Now, the inductance of a loop is calculated by the following formula.
L= μ0 μr N2 A
l
Where,
L = Inductance, H
μ0 = Permeability of free space, Hm-1
μr = Relative permeability
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ELEC120/123 Design Assignment 2018-19

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N = Number of turns
A = Cross-sectional area, m2
l = length of loop, m
In case of rectangular loop the length is given in Table 2 and the width is assumed to be uniform length of 0.1 m.
Now, the cross sectional area = length * width is calculated for different number of turns ( Mocholí-Salcedo et al.
2017). The permeability of free space = 1.257 * 10^(-6) H/m. Now, the material which is used to make the loop
is assumed to be copper. The relative permeability of copper is 1. Hence, the inductance is calculated for
rectangular loop for different lengths and different number of turns as given the Table 2 below.
Similarly, for making the circular loop it is also assumed that the material used is copper and hence the relative
permeability is 1. The cross sectional area is of the loop is A = π D2
4 . The length of the loop is the diameter of the
circle. The calculated values of inductances are shown in Table 3.
From the tables it is clear that in case of rectangular loop the loop inductance do not change with change in
length of rectangle, however, due to non-linear term in the circular loop the loop inductance increases with the
increase in loop diameter (Ren, Yang and Ren 2017). Hence, field intensity will be high and uniform for circular
loop than the rectangular loop. Thus the best option for a traffic light sensor system is to use a circular loop with
large enough diameter such that any disturbance in the magnetic field can be easily detected.
Other designs
The other types of shapes that are prescribed as an induction loop are a cut corner rectangle with spoke and a
diagonal square as given in the end of Table 1. The diagonal square has a triangular field intensity curve through
the length and the cut-corner rectangle with spoke has maximum intensities at the start and the end of shape
length. The cut-corner rectangle with spoke can be used to detect bicycles early or as soon as the vehicle enters
in the magnetic field (Bakker et al. 2015). The diagonal square shape can be used for detecting the bicycles in
the midway of length of shape. The former is appropriate where early detection is necessary and the latter is
appropriate where accurate detection is necessary. These two shapes are not better in terms of applicability as
the provided circular shape has uniform magnetic field intensity thus detection will be same anywhere inside
the magnetic field. However, the diameters of the circle needs to be large to create a significant signal that will
trigger the circuit in the signal controller cabinet.
Conclusions
Thus from the above calculations and designs the best shape for induction loop is a hollow circle as the magnetic
field intensity for circular loop is uniform and thus the detection signal will be uniform anywhere inside the
magnetic field. For rapid detection the bicycles needs to be made of ferromagnetic materials like steel, cobalt or
nickel. Also, there should be some speed limit in the street crossing such that the magnetic loop sensors have
enough time to react on the presence of bicycles. This is because if the bicycle is in high speed the time required
to build significant opposing magnetic field to the main magnetic field is less and thus the circuitry may not
detect the vehicle due to low signal. Thus there should be some specific speed limit such that every bicycle can
be accurately detected.
The induction loop technology is useful for parking areas where sensors can detect the vehicle arriving or
leaving the parking zone. In airports also flights entering or leaving the runway can be detected using induction
loop technology. Induction loop can be used in metro stations where arrival or leaving of trains from stations
can be detected and signals can be displayed for convenience of people.
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References
Bakker, R.M., Permyakov, D., Yu, Y.F., Markovich, D., Paniagua-Domínguez, R., Gonzaga, L., Samusev, A., Kivshar,
Y., Luk’yanchuk, B. and Kuznetsov, A.I., 2015. Magnetic and electric hotspots with silicon nanodimers. Nano
Letters, 15(3), pp.2137-2142.
Fhwa.dot.gov. (2019). Table of Contents - Traffic Detector Handbook: Third Edition—Volume I - FHWA-HRT-06-
108. [online] Available at: http://www.fhwa.dot.gov/publications/research/operations/its/06108/index.cfm
[Accessed 2 Apr. 2019].
Mocholí-Salcedo, A., Arroyo-Núñez, J.H., Milián-Sánchez, V.M., Palomo-Anaya, M.J. and Arroyo-Núñez, A., 2017.
Magnetic field generated by the loops used in traffic control systems. IEEE Transactions on Intelligent
Transportation Systems, 18(8), pp.2126-2136.
NC Bike Ed. (2019). Detection of Bicycles by Quadrupole Loops at Demand-Actuated Traffic Signals. [online]
Available at: http://humantransport.org/ncbikeed/?page_id=44 [Accessed 2 Apr. 2019].
NC Bike Ed. (2019). How to Turn Signals Green. [online] Available at: http://humantransport.org/ncbikeed/?
page_id=37 [Accessed 2 Apr. 2019].
Ren, J., Yang, L. and Ren, J., 2017, August. Study on spatial magnetic field intensity distribution of rectangular
permanent magnets based on Matlab. In 2017 International Applied Computational Electromagnetics Society
Symposium (ACES) (pp. 1-2). IEEE.
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