Assistance/clarification needed as I study

[EhmayWuntee P.E.]

Oh boy, less than a week to go, hopefully things turn out well....

So I worked on the PM portion of my last practice exam and have a few questions:

1) I had a problem that asked for the optimal cycle length using Webster's Theory and my question involves the Total Lost Time and what is involved in it.
It was 4 phases with amber clearance time of 4 seconds each phase and then a sentence saying "Assume lost time per cycle = 3 seconds."

I took this is 4*4 + 3 = 19 seconds of total lost time, but the solution just used 4*4 = 16 seconds.
Is it not correct to add the extra 3 seconds?
I thought the text said something about adding a few things together to get TOTAL lost time, but if it is pretty much always just: # Phases * Time per phase then I suppose I will ignore the rest.
The 3 seconds were not used anywhere in the solution.

2) One question was asking for recommended superelevation percent given the radius, maximum permitted superelevation and speed.
It basically straight up says to use the PGDHS at the very end which means to turn to the graph and get the % in like 10 seconds.
Will the PE actually ask anything like this to where it gives the exact reference to use (other than maybe MUTCD rules)?

3) This one I am pretty sure is a wrong answer/solution or I am missing errata, but I will ask anyway (and update the author if you agree).
It wants to know the sight distance for a stopped passenger car on a one lane minor street that will turn left onto a 2 lane major street.
This would be Case B1 and needs the time gap which according to 2 tables i looked at, say it is 7.5 seconds plus .5 seconds for the extra lane = 8.0 seconds.

The solution claims it is 8.0 seconds plus .5 seconds = 8.5 seconds and references the Green Book which is one of the 2 tables i checked and currently both are printed with 7.5 seconds initially.
Am I correct that an error was made and it should indeed be 7.5 +.5 = 8 seconds for the time gap?

4) My last question involves pavement widening; do you always use the highest value in the range given in the tables for clear zone distance?
I figured it would be a best judgement call depending where your values lie, kind of like interpolating unless it asks for max or safest distance.
An example in the AIO textbook made the most extreme case in that it said find the MINIMUM distance and still used the highest initial clear zone distance which really throws me off.
I don't see why they would have a range if everything seems to use the upper end anyway.

Thanks again for your continued help!

 

[youngmotivatedengineer]

For number 1) the 3 second lost time per cycle should be included. For question 3), what is the date of the practice exam and your reference tables? It sounds like it may be a case of an out dated table or exam question. 

 

[EhmayWuntee P.E.]

For number 1) the 3 second lost time per cycle should be included. For question 3), what is the date of the practice exam and your reference tables? It sounds like it may be a case of an out dated table or exam question. 

Thanks for the quick reply!

So just to verify on #1, I assume not every problem will necessarily state an extra time per cycle (in this case 3 seconds), but if it is there, then I need to always add it to the amber phase time to get the full total lost time.
To be honest, I am not quite sure what the 3 seconds per cycle really is used for or how it would fit in, but either way since it stated it was a lost time, I included it during my solution.

In regards to #3, the practice exam is the second printing of a 2015 which was supposed to have errors corrected (who knows what else was wrong previously). (Here is an amazon link)
I used both the All-in-One third edition (latest edition) and later, checked the Green Book 2011 6th edition (latest edition) to find the exact same table.

 

[ptatohed]

Oh boy, less than a week to go, hopefully things turn out well....

So I worked on the PM portion of my last practice exam and have a few questions:

1) I had a problem that asked for the optimal cycle length using Webster's Theory and my question involves the Total Lost Time and what is involved in it.
It was 4 phases with amber clearance time of 4 seconds each phase and then a sentence saying "Assume lost time per cycle = 3 seconds."

I took this is 4*4 + 3 = 19 seconds of total lost time, but the solution just used 4*4 = 16 seconds.
Is it not correct to add the extra 3 seconds?
I thought the text said something about adding a few things together to get TOTAL lost time, but if it is pretty much always just: # Phases * Time per phase then I suppose I will ignore the rest.
The 3 seconds were not used anywhere in the solution.

2) One question was asking for recommended superelevation percent given the radius, maximum permitted superelevation and speed.
It basically straight up says to use the PGDHS at the very end which means to turn to the graph and get the % in like 10 seconds.
Will the PE actually ask anything like this to where it gives the exact reference to use (other than maybe MUTCD rules)?

3) This one I am pretty sure is a wrong answer/solution or I am missing errata, but I will ask anyway (and update the author if you agree).
It wants to know the sight distance for a stopped passenger car on a one lane minor street that will turn left onto a 2 lane major street.
This would be Case B1 and needs the time gap which according to 2 tables i looked at, say it is 7.5 seconds plus .5 seconds for the extra lane = 8.0 seconds.

The solution claims it is 8.0 seconds plus .5 seconds = 8.5 seconds and references the Green Book which is one of the 2 tables i checked and currently both are printed with 7.5 seconds initially.
Am I correct that an error was made and it should indeed be 7.5 +.5 = 8 seconds for the time gap?

4) My last question involves pavement widening; do you always use the highest value in the range given in the tables for clear zone distance?
I figured it would be a best judgement call depending where your values lie, kind of like interpolating unless it asks for max or safest distance.
An example in the AIO textbook made the most extreme case in that it said find the MINIMUM distance and still used the highest initial clear zone distance which really throws me off.
I don't see why they would have a range if everything seems to use the upper end anyway.

Thanks again for your continued help!

2.)  Here you call it PGDHS (AASHTO's 'A Policy on Geometric Design of Highways and Streets').  Later you call it the Green Book.  I think it would be less confusing to use a consistent name.  I typically call it the GDHS which is the code AASHTO uses in their bookstore.  But, yes, it is common for the exam to list the reference you should obtain the answer from.  From what I remember, if it was incredibly obvious which source to use (ex. using the GDHS for a superelevation question), the exam didn't specifically call out the reference to use.  But you could see mention of the HCM, HSM, RDG, GDHS, etc. in the question itself.  But, regardless, you should know these references well and know in your head if you see a CMF question - use the HSM, if you see a barrier question - use the RDG, etc., etc. 

3.)  For this one, is there a median on the major highway?  And when you say '2 lane major street', I assume you mean 2 lanes in each direction so really a four lane major highway?  Likewise, the minor approach road would be a two lane highway, not one.  Anyway, perhaps the extra 0.5s is for a median? 

4.)  I'd need to know how the question is worded and what they are asking for.  Are you referring to the RDG when you say 'the tables for clear zone distance'?  As a general rule, you would design for the most CZ distance possible.  I see what you are saying with the question using the word 'minimum' but I'd still like to know more question details. 

 

[EhmayWuntee P.E.]

2.)  Here you call it PGDHS (AASHTO's 'A Policy on Geometric Design of Highways and Streets').  Later you call it the Green Book.  I think it would be less confusing to use a consistent name.  I typically call it the GDHS which is the code AASHTO uses in their bookstore.  But, yes, it is common for the exam to list the reference you should obtain the answer from.  From what I remember, if it was incredibly obvious which source to use (ex. using the GDHS for a superelevation question), the exam didn't specifically call out the reference to use.  But you could see mention of the HCM, HSM, RDG, GDHS, etc. in the question itself.  But, regardless, you should know these references well and know in your head if you see a CMF question - use the HSM, if you see a barrier question - use the RDG, etc., etc. 

3.)  For this one, is there a median on the major highway?  And when you say '2 lane major street', I assume you mean 2 lanes in each direction so really a four lane major highway?  Likewise, the minor approach road would be a two lane highway, not one.  Anyway, perhaps the extra 0.5s is for a median? 

4.)  I'd need to know how the question is worded and what they are asking for.  Are you referring to the RDG when you say 'the tables for clear zone distance'?  As a general rule, you would design for the most CZ distance possible.  I see what you are saying with the question using the word 'minimum' but I'd still like to know more question details. 

2) Yes sorry, I am used to referring to them by their abbreviated letter names and the practice exam solutions will sometimes say Green Book instead so I go with that. They go hand in hand in my head, but certainly may cause others to think I am referring to 2 different books.
I will have to take a closer look at the chapters and layout of the references you listed, which I have all of them and more, but the All-in-One (AIO) has really been a terrific source for almost every question so I just use that and it typically has the equations, tables, or numbers from the other books. I will likely use the AIO for 80% of the questions if it is similar to the NCEES practice exam. Questions regarding the MUTCD will definitely need to reference its own book of code and the others may be needed for more depth or the CERM to help clarify things not in the AIO.

3) No median, undivided 4 lane (2 in each direction) and 2 lane minor street (1 in each direction). Sorry I jumped to using the numbers based on how you would look up the tables and not like the question states. Also for clarity, no mention of grade.
I feel like if there was supposed to be 2 types of 0.5 seconds added, he would have listed them individually and not listed it like the table he pulled it from shows a base value of 8.0. This just really seems like an obvious typo in my opinion.

4) I think this got explained well when I asked a co-worker about it randomly. The design, like you said, is to have the most CZ distance possible, but if there happens to be a scenario such as limited ROW, you can justify going a touch smaller by using the range they offer, but always plan for the max possible.
They also pointed out that there is a head-wall on the outside shown in the diagram so once again you want the most CZ distance you can get from it.
I think I am fine just trusting to always use the highest value in the given range as the initial base unless you can find proof to need to drop one or two feet.

 

[ptatohed]

2.)  That's good that the AI1 is helping out so much.  But be careful relying too much on the AI1 or CERM for all your PM stuff (they'll be fine for all your AM).  You should know the more notable NCEES Transpo resources pretty well.  You can let the asphalt books go. 

3.)  Yeah, you are right.  Even if there was a reason to add an additional .5s (like, say, a median), it should be broken out as 7.5 + .5 +.5 like you said.  I was just trying hard to find some justification for the 'mystery' .5s. 

4.)   

 

[EhmayWuntee P.E.]

So I found out that the Greenbook (PGDHS) is pretty tricky to look up a few things. When I went to redo my PM portion of the NCEES exam, I had trouble finding 2 pages that I remember finding previously (or found at least one of them before). I think this time around I relied on the small index too much and needed to look at the TOC more. Obviously I can tab these pages now, but its the principle that I am worried about, not finding another needed page because it isn't indexed well.

The pages I had trouble finding were ramp width and acceleration lane length and am surprised the most that acceleration lanes were not in the index. Is there a recommended method to looking things up in this book or is it to just be a bit better familiar with the chapters and what is inside them even though some are over 100 pages long?

 

[EhmayWuntee P.E.]

I guess you can't edit posts here?

I just wanted to add that I happened to look at the 2004 Greenbook that I have at work and it's index is much better and had both topics super easy to find. It's a shame the 2011 is inferior in terms of its indexing...

 

[ngmakhlo_PE]

So I found out that the Greenbook (PGDHS) is pretty tricky to look up a few things. When I went to redo my PM portion of the NCEES exam, I had trouble finding 2 pages that I remember finding previously (or found at least one of them before). I think this time around I relied on the small index too much and needed to look at the TOC more. Obviously I can tab these pages now, but its the principle that I am worried about, not finding another needed page because it isn't indexed well.

The pages I had trouble finding were ramp width and acceleration lane length and am surprised the most that acceleration lanes were not in the index. Is there a recommended method to looking things up in this book or is it to just be a bit better familiar with the chapters and what is inside them even though some are over 100 pages long?

For the references such as the HCM, the HSM, MUTCD, etc. I tabbed the hell out of them and practiced and practiced relying solely on the tabs and my memory of where I could find each table, chart, or whatever it was I needed. It is VERY important that during the exam you clear your mind, stay calm, and focus only on the problem at hand. Do not start thinking back to a problem you saw previously or anticipating one you saw ahead. Read the problem carefully, think to yourself what category does that question fall under in regards to the NCEES exam layout and think what reference will get you to the topic that the question pertains to. Keeping calm and thinking carefully is important.

Best of luck!

 

[EhmayWuntee P.E.]

I wanted to take a moment to thank all of you who helped answer my questions/clarifications during my self study.

I just found out that I passed and I am sure you guys assisted in a few of my correct answers.

 

[ptatohed]

I wanted to take a moment to thank all of you who helped answer my questions/clarifications during my self study.

I just found out that I passed and I am sure you guys assisted in a few of my correct answers.

)