40
M. L. de Barros Baltar et al.
the traffic conditions of the road, when an incident occurs, part of the flow overcomes the bottleneck while another part is retained, forming a queue of non-recurring
congestion.
Therefore, it was necessary to define how many vehicles passed through the incident and how many stayed in the traffic congestion queue (q). So, let f be the regular
traffic flow at the time of the incident and C be the road capacity that is reduced in
the section under study during the incident’s time. If f ≤ C, there is no nonrecurrent
congestion due an incident, but the speed can be reduced. In this scenario, when
there is an incident, the emission calculation is performed according to Eq. (2). The
values of e pc , e t and e b are obtained using Eq. (1) with their correspondent constants
according to vehicle types.
E tot1 = t × f ×
% f pc × e pc + % f t × e t + % f b × e b
(2)
where:
• t is the time duration of the incident;
• % f pc is the percentage of the passenger cars in the traffic composition;
• e pc is the passenger car emission rate;
• % f t is the percentage of the trucks in the traffic composition;
• e t is the truck emission rate;
• % f b is the percentage of the bus in the traffic composition; and
• e b is the bus emission rate.
However, if f > C, there are traffic congestion queue in such way that the size
(q) can be estimated from the Queuing Theory [19], according to Eq. (3). The result
of this equation is the number of vehicles in queue.
q = | f t| − |
t −
1
f
C|
(3)
For this case, the total emission will be calculated according to Eq. (4). The
parameters are the ones presented before.
E tot2 = q ×
% f pc × e pc + % f t × e t + % f b × e b
+ t × C ×
% f pc × e pc + % f t × e t + % f b × e b
(4)
Equations (2) and (4) seek to estimate the CO 2 emissions considering the occurrences of incidents. The first equation is used if the incident does not increase the
recurrent queue and the second one is used if a queue is generated by the capacity
reduction at incidents.
To understand the difference in CO 2 emissions with and without incidents, it is
necessary to compare the two scenarios, as proposed in Stage 4 of the methodology
presented in Sect. 2. As the total emission increases over the time (the higher the
duration considerer, higher is the emission), was considered the same duration time
M. L. de Barros Baltar et al.
the traffic conditions of the road, when an incident occurs, part of the flow overcomes the bottleneck while another part is retained, forming a queue of non-recurring
congestion.
Therefore, it was necessary to define how many vehicles passed through the incident and how many stayed in the traffic congestion queue (q). So, let f be the regular
traffic flow at the time of the incident and C be the road capacity that is reduced in
the section under study during the incident’s time. If f ≤ C, there is no nonrecurrent
congestion due an incident, but the speed can be reduced. In this scenario, when
there is an incident, the emission calculation is performed according to Eq. (2). The
values of e pc , e t and e b are obtained using Eq. (1) with their correspondent constants
according to vehicle types.
E tot1 = t × f ×
% f pc × e pc + % f t × e t + % f b × e b
(2)
where:
• t is the time duration of the incident;
• % f pc is the percentage of the passenger cars in the traffic composition;
• e pc is the passenger car emission rate;
• % f t is the percentage of the trucks in the traffic composition;
• e t is the truck emission rate;
• % f b is the percentage of the bus in the traffic composition; and
• e b is the bus emission rate.
However, if f > C, there are traffic congestion queue in such way that the size
(q) can be estimated from the Queuing Theory [19], according to Eq. (3). The result
of this equation is the number of vehicles in queue.
q = | f t| − |
t −
1
f
C|
(3)
For this case, the total emission will be calculated according to Eq. (4). The
parameters are the ones presented before.
E tot2 = q ×
% f pc × e pc + % f t × e t + % f b × e b
+ t × C ×
% f pc × e pc + % f t × e t + % f b × e b
(4)
Equations (2) and (4) seek to estimate the CO 2 emissions considering the occurrences of incidents. The first equation is used if the incident does not increase the
recurrent queue and the second one is used if a queue is generated by the capacity
reduction at incidents.
To understand the difference in CO 2 emissions with and without incidents, it is
necessary to compare the two scenarios, as proposed in Stage 4 of the methodology
presented in Sect. 2. As the total emission increases over the time (the higher the
duration considerer, higher is the emission), was considered the same duration time