to tailgate, tailgating 
[verb]
[bum-per-kle-ven, bum-per-kleef-de, h. ge-bum-per-kleefd]
"Bumperkleven" is composed of "bumper" and "kleven", which respectively translate to "bumper" and "to stick". Hence literally, "bumperkleven" would translate to "to bumperstick" or "bumpersticking". In English, this is called tailgating: the practice of driving on a road too closely at a distance which does not guarantee that stopping to avoid collision is possible. [from Wikipedia]. A person who is tailgating is called a "bumperklever".
"Bumperkleven" is an example of a compound verb that cannot be separated when conjugated. So:
>> [correct] ik bumperkleef, ik bumperkleefde, ik heb gebumperkleefd
>> [incorrect] ik kleef bumper, ik kleefde bumper, ik heb bumpergekleefd
Examples:
– "Irritant als mensen bumperkleven."
("De vertaling van bovenstaande zin.")
– "In geval van bumperkleven kan de politie je een bekeuring opleggen."
("In case of tailgating, the police may give you a fine.")
– "Wat zullen we nou krijgen! Ik rij al 150 en die gast is nu al vijf minuten aan het bumperkleven."
("What's going on here?! I'm driving 150 (km/h) already, and this dude is tailgating me for five minutes now.")
Expressions:
– "Haastige spoed is zelden goed": (lit.: hasty haste is seldom good) haste makes waste.
Related words:
– Auto: car [noun] [de auto, de auto's].
– Bumper: bumper [noun] [de bumper, de bumpers].
– File: traffic jam [noun] [de file, de files].
– Kleven: to stick [verb] [kleven, kleefde, h. gekleefd].
Example:
– "Er kleeft kauwgom aan de onderkant van de tafel."
("There's chewing gum sticking under the table.")
Kleven has a very similar word in English… “to cleave to (something)”, which means to stick or cling to something. This is distinct from “to cleave” (without the “to”) which means to split apart.
A better translation of this:
Ik rij al 150 en die gast is nu al vijf minuten aan het bumperkleven.”
I’m already doing 150 (km/h), and this dude has been tailgating me (or “has been on my tail”) for five minutes now.”)
Better to put already before the verb in English, and “to do 150′ fits the colloquial sound of the sentence better, and you need to say ‘he has been tailgaiting’ rather than “is”