On a length of road, when two lanes of traffic merge into one and there are no lane markings, this is known as zip merging.
How to merge?
As per the rule, any vehicle which reaches the merge point first, has the right to go. In a simple term, when two lanes are merging and two cars are approaching the merge point and car A is ahead of car B, car A has the right to go. Please see image below.
You are driving in a RIGHT lane, Mr. X is driving in LEFT lane. When you are approaching merge point, Mr. X's vehicle is ahead of your vehicle. You must give way to Mr. X and do the right thing.
You are driving in a RIGHT lane, Mr. X is driving in LEFT lane. When you are approaching merge point, Your vehicle is ahead of Mr. X's vehicle. You have the right to go and Mr. X will give you the way.
Important to Remember
When merging at a ZIP merging, you must indicate appropriately.
If you are in a LEFT LANE indicate RIGHT.
If you are in a RIGHT LANE indicate LEFT.
You must always look at the outside mirror which ever side you are merging from. If from left lane the check right mirror and from right lane check left mirror.
You must do a head check for any blind spot over your shoulder.
In the real world, this RULE IS NOT FOLLOWED by road user and a CLASH occur on the road. To avoid the clash, do the right thing by staying back ang giving way to the impatient and ignorant driver.
ZIP MERGING SHOULD BE DONE WITH CAUTION AS MOST ROAD USER ARE NOT AWARE OF IT.