Thanks for the reply.  All track and turnouts are Atlas Code 80 track.  The engines are one Atlas and one Bachmann; the Bachmann is a GP 40 series, the Atlas a GP38.  Interesting that the derailment seems to occur as the rear carriage is crossing.  The front carriage appears to be making the turn properly.  I'm afraid the answer is what you stated about a turnout immediately following a tight curve.

I've been plagued with frequent derailments which occur on 2 code 80 remote switches; one right and one left.  Both are positioned after 9" radius curves.  When in the  switch position my diesels are prone to derail going into the turn.  Is this possibly a function of switching, the potential for derailing? Are the curve radii too tight? Are diesel engines prone to derail? Using both atlas and Bachmann engines. Checked track alignments, slow engine speeds, cleaned tracks etc.  Any thoughts?

Thanks.  Will check.

Thanks to both responders.  Forgive my lack of nomenclature identification.  Before ballasting and before nailing down track I checked all blocks, and turnouts, for proper connection and functioning.  For whatever reason after ballasting I found a dead spot within one block.  However the dead spot occurred in the remote RH turnout. The terminal connector for this block is supplying current to the track.  I have a simple current tester (light bulb).  Within the turnout I lose power.  I have power to the common rail thru the entire block when the  tester is linked to a control rail outside the block.  The problem is in the control rail within the turnout.  Imagining a Y with 2 branches attached to a stem, I have power on the left branch above the junction with the stem.  The right branch is dead as is the stem of the Y.  Since I do not wish to rip apart the ballasted track and since the turnout works fine otherwise, I have decided to connect another terminal connector to the control rail and set this up as a separate block.  I still don't understand why there is a power loss on the control rail IN the turnout.  It is an older Atlas remote turnout.  Thanks.

Having just finished ballasting I cleaned my tracks and gave my diesel a run to check the electrical conductivity.  Besides some sticky remote turnouts the major problem I encountered is the loss of power in one segment.  This is an isolated segment with a terminal joiner and plastic rail connectors.  The power loss appears to happen at the remote switch.  I have verified power between the terminal connector and track to the turnout. I have power in the common rail. However my tester shows no power on the track and turnout past the insulators.  Have I some how shorted out my power at the remote turnout during the ballasting process?  I would appreciate any thoughts.

Thanks for sharing  .

I have watched almost every you tube video on ballasting.  But I am running into a problem.  After laying down the ballast, when I wet down the ballast and apply the cement (woodland scenic) with an eye dropper I keep getting ballast particles winding up on the track ties.  I am sure that I am removing all ballast from the ties prior to gluing.  Also I have noticed that the cement when applied tends to reshape the ballast.  I am applying the cement carefully, down close to the track.  My wet water contains dish detergent as stated in numerous videos.  Any suggestions how I can get a smoother result when applying glue or what I may be doing wrong?

If a question has been asked and answered to my satisfaction is it possible to delete that question?  I have tried by hitting delete and get a message that states "you cannot delete topic in this forum."  Do questions/topics stay forever?

Thanks for the reply.

Thanks Len.  So train direction controlled by separate cabs in each block can be similar or opposite.  Seems the Atlas selector keeps things right.

I'm running into a mental block concerning DC polarity.  I am setting up for 2 cab operation, and for purposes of understanding my question, let's say I have 2 basic ovals connected by turnouts. I have placed plastic rail joiners to create separate blocks, connected everything to an Atlas selector etc; where I am getting hung up is while I am using separate cabs to control Train A on the outer oval and Train B on the inner oval mustn't they always run in the same direction due to the polarity of the control and common tracks?  In other words when you change direction of Train A aren't you changing the polarity of the common rail, so that the polarity of the common rail would conflict with the polarity of the common rail controlling Train B?  Am I making this too complicated for myself?  My hobby shop guy says the polarity only changes on the control rail.  Diagrams in the Atlas wiring manual show positive and negative rails. Some track plans (Atlas) in discussing turnouts specifically talk about "opposing trains."  Any clarification is appreciated. 
PS there are no wyes or reversing loops in my layout.

Things seem to get more complicated as I wander deeper into the hobby.  Re couplers: Does anyone  care to weigh in on which brand of couplers are most universal in terms of working with different train makers?  I like the idea of using magnetic couplers but noted several manufacturers now supply their magnetic couplers on their products e.g., Bachmann, Atlas etc. and of course MTI.  I currently have dummy knucklers on my Bachmann cars and rapidos on older rolling stock.  Would like to standardize my couplers, though not every car needs magnetics.  Any thoughts on how to simplify replacements? I have seen a You Tube video comparing couplers but don't think he talked about compatibility. 

Which model diesels (DC only) are the latest Bachmann models?  Having had the experience of finding that the motor for my GP 40 diesel is no longer available, I have no desire to be in the position of needing parts only to find out that they are no longer in production.

Thanks spookshow, will do tomorrow morning.

yes  that's it exactly.  I'll give it a shot.  I do think given some other problems I wrote about recently that I would like to replace the motor, but that may not be possible since the online parts store says they are sold out.  I need to call Bmann and clarify what that means exactly.  I will be very disappointed if they are discontinuing replacement parts for that model, GP 40 series.  Thanks for your help.