#density

[@betu2010kiit]

Sir, Very pertinent and information video! Surely will be helpful for the viwer.

[@SatishIITR]

Thanks, Please circulate the link in your groups.

[@rameshdhimal3428]

Which capacity did you use?? First you determined capacity for each direction and sum two way capacity and used that for analysis??? Or you use capacity of one direction at a time for analysis in case of undivided two lane two way urban midblock section ???

[@SatishIITR]

For a two lane - two way roads, we do not determine directional capacity. Traffic data are collected for the total traffic in two directions and then analyzed. Directional movements are analyzed only for multilane divided highways.

[@rameshdhimal3428]

What about 4 lane undivided 2 way road road??? But road has central longitudinal line marked..

[@SatishIITR]

@@rameshdhimal3428 you can do both ways - individual direction or total for both. But Capacity will be expressed per lane per direction only

[@rameshdhimal3428]

Sir, how did you find the relation between friction variable and reduction in capacity??? Reduction in capacity for non base section was determined from the model developed for base section with varying carriageway width... I counted the frictions on 5 min interval on each site.... Now should i average all friction value on entire observation on each site and find relation with reduction in capacity ??? Or use average flow and friction on 5 min interval and find relation with reduction in capacity???

[@SatishIITR]

write separately to Dr. Subhadip for answers to these queries.

[@muhammadzaidhasan1426]

Sir, in the area occupancy to density conversion , have you taken different average size of vehicle for every observation period.?

[@SatishIITR]

once you know the occupancy (percent or ratio) then size of the vehicle does not matter. Take size of standard car to get it pcu

[@rameshdhimal3428]

How to determine PCU value for vehicles in urban mid block section beside your's method?? I have tried multiple linear regression method where mean speed of car were regressed against flows of each vehicle type but found some value negative and some positive ....

[@SatishIITR]

Linear Regression should not be used as it is based on the method of least error and the analyst has no control on sign of coefficient. You can use headway method if you have proper data.

[@rameshdhimal3428]

Sir what would be the number of snapshots required in case of trap length around 30-60m??? What to do if platoon and Queue occured in our snapshot time interval?? Should we ignore that time interval or take other random snapshot ???

[@rameshdhimal3428]

which value to take if road in empty in that time interval?? if taken one snap at 20 sec interval...

[@SatishIITR]

There is no thumb rule which can give you the number of snapshots. Density is difficult to measure in field and that is why most of the time it is calculated from Q = KV, speed and flow are easy to get from field observation.

[@rameshdhimal3428]

@@SatishIITR doesn't this formula work only in uniform flow of traffic???.. but in case of interrupted and disturbed flow where there is platoon and queue which we need to ignore ....and these value would give more capacity ...

[@rameshdhimal3428]

Sir, i measured the speed and flow of traffic for 5 min interval... now to find capacity using greenshield model....then i plotted speed and density graph.... For density what i did was k=q/v... can we do this instead of finding capacity from speed and flow graph???

[@rameshdhimal3428]

Sir, how to draw a complete parabola as in Greenshield model in speed and flow plot of graph of traffic???

[@SatishIITR]

Develop a relation (straight line) between speed and density from field data. If you have collected speed and volume data then find density using Q = KV. Use this equation (speed - density) to get speed value at varying value of K (starting with zero to almost jam density), in an Excel sheet. determine traffic volume Q in the next column using Q = KV. Plot speed volume curve.

[@chiranjeevitadi2417]

Sir Excellent Presentation and very Informative video Sir, Please post the video related to Traffic Signal design

[@SatishIITR]

Ok, will prepare. please circulate the link in your groups also.

[@rameshdhimal3428]

Sir how should the maximum flow (capacity) be calculated??? I have extracted data of space mean speed ( km/h) and flow (PCU/h) at 1 minute interval for 1 hour... I have collected data for 1 hour in off peak hour from 11 -12 pm in different urban midblock section of undivided 4 lane 2 way road...i need to make model of variation in carriageway width and capacity in ideal road condition where there is no friction like pedestrian, parking, unparking, bus stops, etc... also I need to find capacity of road in case of presence of road side friction or disturbances in other riad midblock section....in disturbed traffic condition, i measured traffic flow and space mean speed... now the problem is how to find capacity???

[@SatishIITR]

Use following steps to get the capacity of a section. 1. Speed - flow data, calculate K, using the relation q = kv 2. Plot speed density curve and develop a straight line equation. 3. using this equation make a table (in MS Excel) between speed and density - Take density from very low to very high at some interval (may be 5) 4. Now you have speed data at different density levels (theoretical). Calculate flow, using q = kv 5. Plot speed - Flow curve and get the capacity

[@rameshdhimal3428]

Sir, isn't directly the maximum flow could be obtained from the speed and density plot by finding linear equation in v = a - bk and free flow and jam density determined as vf = a km/h and kj = vf/b and then max flow = vf* kj/4

[@rameshdhimal3428]

Sir, Can you please send me thesis of phd of topic " side friction paramters and its influence on urban undivided road " ?

[@SatishIITR]

I do not have soft copy of this Ph.D. thesis as it was completed when I was on leave from IIT Roorkee. You can contact Dr. Subhadip Biswas who is faculty at NIT Silchar now, at [e-mail]

[@priyeshbhavsar7461]

Respected sir, This video is so much informatroy. Its my humble request deliver one session on " Acceleration and speed relationship on multilane highway" which is published by you.

[@SatishIITR]

Thanks Priyesh for this suggestion, I will certainly do it soon.

[@rameshdhimal3428]

Sir, i have plotted speed vs density from the extracted data of speed and flow and using formula of k = q/v. The maximum flow obtained is good but R square value is between 0.3 to 0.5 for base section... For each site, I have 1 hour data and data was collected for 1 min interval ... so total 60 data for each site... what should I do sir to increase R square value while maintaing maximum flow( capacity ) same???

[@SatishIITR]

No standard specify one minute time interval for data collection. It should at least be 5 min. One minute data will produce lot of noise and that is why your R squared value is low. One hour data is too less to give any range of traffic volume on a road. go at least for 6 hours field observation,

[@rameshdhimal3428]

Sir, i measured the speed and flow of traffic in 5 min interval for 1 hour data....now to find capacity using greenshield model....i plotted speed and density graph.... For density what i did was k=q/v... can we do this for finding density??? Is this the correct way to find density??? In speed vs flow curve, i could not find the maximum flow (capacity) due to limited number of data... in 1 hour i have only 12 set of data .. i.e. 60 min/5min = 12... the R square value for quadratic fit is very very low.... but in speed vs density( k=q/v) the linear fit of the line shows good R square value....

[@SatishIITR]

Yes you can find density using the relation Q = KV. But you cannot draw any inference from 12 data points. The capacity value will just be absurd even if you get a good R squared value for linear relation between speed and density. It is because 12 data points do not represent flow conditions at site. You need at least 4-6 hours data to get the meaningful results.

[@vijayamritraj3555]

Sir, I calculated the traffic density using n-t method of a video having duration 2.30 minutes and taken 5 sec time interval for that. And calculated density for each time interval. Now I have to give a single density for the whole duration, how I will give ?

[@SatishIITR]

why for 5 sec interval? you should have done it for 2.30 minute and got the density.

[@vijayamritraj3555]

Okay sir

[@rameshdhimal3428]

Sir, i have plotted three diagram and found different R square value... why is it so?? I have speed and flow data of traffic.... then i determined density as k = q/v... i plotted speed vs density (R2= 0.51), speed vs flow ( R2= 0.1611) and flow vs density( R2 = 0.91)... which R square value should be taken???

[@SatishIITR]

Please discuss with your supervisor as why are you getting such a large variation in the R squared value. I cannot tell you the reason without going through your entire analysis.

[@rameshdhimal3428]

Sir, i was reading your paper of 2020 on "Side friction parameters and their influences on capacity of Indian undivided urban streets." and trying to do similar research. Sir, how did you take the speed and flow of the vehicles in case when parking and unparking maneuvers take place as they causes traffic to halt or slow by acceleration or deceleration?? Did you considered speed and flow in traffic stoppage condition due to frictions or only take the speed and flow ignoring those which causes complete stoppage and slow due to accelerating or decelerating in case of non-base section???

[@SatishIITR]

Haha, I cannot write the whole procedure here, but if I remember correctly (this was the Ph.D. research work of one student), we did it by collecting the data of speed and flow over a period of time in different levels (read intensity) of parking and unparking movements in a certain length of the road.

[@rameshdhimal3428]

Sir, i have been manually measuring the speed and flow from video... is there any freely available software ???

[@SatishIITR]

I think yes, Let me check with my students if any of them have it.

[@rameshdhimal3428]

Sir can you share this research paper to me???

[@SatishIITR]

This is not the research paper, It was a M. Tech thesis work which is put in PPT form.

[@rameshdhimal3428]

Sir, are you available in any social media or viber or whatsapp or messenger??

[@SatishIITR]

No Dear, I am not active on any social media other than LinkedIn