3 legged intersections custom

T-Intersections

To create a T-intersection you will need 4 individual blocks, each named to indicate which approach is not present, e.g. "No NB" indicates an intersection where the northbound approach is "missing".

Each Intvol block must contain the following attributes:

ATTRIBUTE ORDER	ATTRIBUTE TAG NAME	NO NB APPROACH	NO SB APPROACH	NO EB APPROACH	NO WB APPROACH

1	ID	ü	ü	ü	ü
2	NBL	û	ü	û	ü
3	NBT	û	û	ü	ü
4	NBR	û	ü	ü	û
5	SBL	ü	û	ü	û
6	SBT	û	û	ü	ü
7	SBR	ü	û	û	ü
8	EBL	ü	û	û	ü
9	EBT	ü	ü	û	û
10	EBR	û	ü	û	ü
11	WBL	û	ü	ü	û
12	WBT	ü	ü	û	û
13	WBR	ü	û	ü	û
14	NB	û	ü	ü	ü
15	SB	ü	û	ü	ü
16	EB	ü	ü	û	ü
17	WB	ü	ü	ü	û
18	NORTHSOUTH	ü	ü	ü	ü
19	EASTWEST	ü	ü	ü	ü

Note: NORTHSOUTH and EASTWEST are optional if you intend to use intersection road names.

If you do intend to use street names, then both NORTHSOUTH and EASTWEST must be included.

The TAG names are critical but the attribute prompts are not and can be defined as anything you like or feel comfortable with.

The attributes MUST be in the order shown above to ensure correct importing of the data.

Although not strictly necessary, we recommend all entities be placed on layer 0. We would also recommend that you use a unique name for your Intvol block Text Style, e.g. “INTVtxt”. This means that if some user later changes the font associated with “Standard” then your blocks will still appear as you originally intended.

First, create your block and arrange it to suit your requirements (do not add any arrows at this stage).

It is easier to follow if you create the “No EB” Intvol block first (the block with the eastbound approach "missing"). This is important as the arrow blocks are created using the “No EB” block.

Attributes:

As you can see from the table above, for the "No EB" block, we have used the following attributes (in order):

ID, NBT, NBR, SBL, SBT, WBL, WBR, NB, SB, WB, NORTHSOUTH, EASTWEST

This is best illustrated in the following sample block graphic (EB approach does not exist):

Un-exploded View	Constructing Block Arrows

Arrows:

Now we are ready to deal with the arrows. You will need a total of three arrows, one for “Left Turn”, one for "Through", and one for “Right Turn”. Place these arrows in the Westbound section as shown in the second graphic above. Note that arrows that are not used in any given T-intersection are "turned-off" as required by the selected geometry. For example, even though TIAH is aware of the WBT arrow, it would not be used in the "No EB" T-intersection block.

Once you are happy with the overall appearance of your Intvol block, run the Wblock command.

Select the entities in turn (do NOT window your selection!), selecting the graphical entities of the Intvol block first, followed by the attributes in the order listed above. This will ensure the attributes are in the correct sequence. Do NOT select the arrows at this stage!

In this example, we have placed two temporary lines to identify the centre of the block for selection purposes only ~ we are not selecting these lines in the block itself.

Select “Convert to Block” while using the Wblock command - this will automatically convert the entities into a block which will allow you to see what the block looks like when inserted.

Now run the Wblock command again for each of the three arrows, selecting the Intvol block centre point (created earlier as a drawing aide) as the insertion point for each of the arrows.

Now follow the procedure above again to create the 3 remaining “No NB”, “No SB", and “No WB” Intvol blocks. You do not need to create additional arrow blocks. The arrows just created are used on all the T-intersection blocks.

Naming Convention:

For the “T” intersections, the Intvol blocks should be named as follows:

INTVOL + T + Orientation + Numeric Identifier

For example:

INTVOLytnonorth01.dwg

INTVOLynosouth01.dwg

INTVOLytnoeast01.dwg

INTVOLynowest01.dwg

The Arrow blocks should be named as follows:

INTVOL + ar + Numeric Identifier + direction

For example:

INTVOLar01L

INTVOLar01R

Each set should contain the same numeric identifier. This allows you to have more than one style of T-intersection to use (arrow set 01 to be used with Intvol 01, etc.)

Place the four completed Intvol blocks into the C:\Program Files\TIAH\INTVOL\3LEG directory and the three completed Arrow block into the C:\Program Files\TIAH\ARROWS\3LEG directory.

The blocks will be recognized the next time you start TIAH 4.