2 Shields Same Direction Different Arrows

[roadman65]

http://www.flickr.com/photos/54480415@N08/8501337385/in/photostream/
If you notice the I-45 NB shield and Hurricane Evacuation shield are pointing in two totally different directions, yet both are being directed to the same route.  The evacuation is via I-45 NB here which is a left under the bridge in the distance hence why TexDOT chooses the straight arrow for I-45 NB as it would really be incorrect to say directly left.  However, for some reason different logic was used when signing the hurricane evacuation trailblazer.

[Brian556]

This one on Denton Tap Rd in S Lewisville has to be the worst and most confusing misuse of arrow plaques ever.
https://maps.google.com/?ll=32.997794,-96.993077&spn=0.000036,0.024784&t=h&z=16&layer=c&cbll=32.997901,-96.993072&panoid=NdHDbGwnzApoz02V1Ho50w&cbp=12,0,,0,0

[agentsteel53]

http://www.flickr.com/photos/54480415@N08/8501337385/in/photostream/
both should be elbow arrows to indicate that the left turn is to be made not immediately, but at the next intersection

there; I wrote that in clear English for ya.

[1995hoo]

http://www.flickr.com/photos/54480415@N08/8501337385/in/photostream/
If you notice the I-45 NB shield and Hurricane Evacuation shield are pointing in two totally different directions, yet both are being directed to the same route.  The evacuation is via I-45 NB here which is a left under the bridge in the distance hence why TexDOT chooses the straight arrow for I-45 NB as it would really be incorrect to say directly left.  However, for some reason different logic was used when signing the hurricane evacuation trailblazer.

Do they ever do the contraflow thing where they reverse one carriageway? If so, could that be part of the rationale?

[roadman65]

http://www.flickr.com/photos/54480415@N08/8501337385/in/photostream/
If you notice the I-45 NB shield and Hurricane Evacuation shield are pointing in two totally different directions, yet both are being directed to the same route.  The evacuation is via I-45 NB here which is a left under the bridge in the distance hence why TexDOT chooses the straight arrow for I-45 NB as it would really be incorrect to say directly left.  However, for some reason different logic was used when signing the hurricane evacuation trailblazer.

Do they ever do the contraflow thing where they reverse one carriageway? If so, could that be part of the rationale?

If they did it would require the SB Service Road to be part of it as there are no direct ramps here to the interstate.   

In actuality both signs are really correct.  It is just inconsistent use of the place cards that makes this really stand out.

[Alps]

A different case - one shield, same direction, different arrows: http://goo.gl/maps/bNUKy

[djlynch]

http://www.flickr.com/photos/54480415@N08/8501337385/in/photostream/
If you notice the I-45 NB shield and Hurricane Evacuation shield are pointing in two totally different directions, yet both are being directed to the same route.  The evacuation is via I-45 NB here which is a left under the bridge in the distance hence why TexDOT chooses the straight arrow for I-45 NB as it would really be incorrect to say directly left.  However, for some reason different logic was used when signing the hurricane evacuation trailblazer.

Do they ever do the contraflow thing where they reverse one carriageway? If so, could that be part of the rationale?

Contraflow doesn't start until north of Conroe. http://ftp.dot.state.tx.us/pub/txdot-info/trv/hurricane/i45_contraflow.pdf

[roadman65]

It is just a case of different contractors installing things differently.  I see many except where the shield will have a bent arrow (either left or right) while the green guide sign next to it with the route's control cities using a straight arrow pointing to the same turn.

I am looking for two shields, though, where one has one type of arrow and the other another both denoting the same turn.

Brian's find is exactly to the point.  He found an excellent example.