Kestral X RRV:
Rapid Response Vehicles play a special role in the Kestral armed forces. They are used as patrol vehicles and first response vehicles by special teams such as Storm Troopers and Field Medics. The RRV is an oversized four wheeled lightly armoured road car.
Type: Wheeled Tactical Speed: 20m
Cruising Speed: 85kph Manoeuvrability: +10
Structural Integrity: 25 Size: Enormous
Armour: Front 20, Side 16, Rear 16
Vehicle Traits: Enclosed, Rugged, Wheeled Vehicle
Crew: 1 Driver, 1 Gunner (Pintle-mounted Weapon)
Carrying Capacity: 5 Imperial Guardsman plus gear

Weapons:
Pintle-mounted weapon (Choose one of the following).
• Heavy Stubber (100m, -/-/8, 1d10+4 I, Pen 3, Clip 80, Rld 2 Full)
• Missile Launcher (300m, S/-/-, *, Pen *, Clip 1, Rld Full)
• Automatic Grenade Launcher (80m, S/2/4, *, Pen *, Clip 20, Rld 2 Full)

Options:
The Pintle-mounted weapons sometimes have a Gun Shield (See page 121 HotE).
A Medi-back variant was introduced to transport injured soldiers quickly to a field hospital, these models sacrifice the Pintle-mounted weapon for the capability to hold two stretchers and an Advanced Medi-kit. These models have their carrying capacity lowered to 2.

Civilian Road Car:
The Road Car is a vehicle used by those who can afford one. They can comfortably get you from point A to point B.
Type: Wheeled Tactical Speed: 18m
Cruising Speed: 75kph Manoeuvrability: +10
Structural Integrity: 16 Size: Enormous
Armour: Front 15, Side 10, Rear 10
Vehicle Traits: Open Topped, Wheeled Vehicle
Crew: 1 Driver
Carrying Capacity: 4 passengers

Small Industrial Flatbed Truck:
These commercial vehicles are used to transport loads throughout the city. Insurgents have been known to add some extra armour and mount on or two machine guns on top of them.
Type: Wheeled Tactical Speed: 15m
Cruising Speed: 65kph Manoeuvrability: +0
Structural Integrity: 26 Size: Enormous
Armour: Front 18, Side 16, Rear 16
Vehicle Traits: Open Topped, Rugged, Wheeled Vehicle
Crew: 1 Driver
Carrying Capacity: 2 passengers and 5 metric tons of cargo

Your civilian road car is more durable than a killer kan.

I would go with Front 12 Sides 10 Rear 12 (baggage compartment!). Structural Integrity around 8.

And 3 AP for the windshield.

I actually didn't any account for any armour on the windshield, hence the open topped rule.
I think I will change the armour to 14/10/10 with a Structural Integrity of 12, otherwise it would have less than a bike.

A Killa Kan still has more Structural Integrity.

14 is a bit much for the front I think. Well, the engine block is there I guess, hmmm.

In the Dark Heresy Beta the Hectin Ground Car has armour 15/10/8. They also have the Chimera in the Beta, with the same armour values as in Only War.

No hit points in the Dark Heresy Beta so that won't help.

Why not delete all armour for civilian vehicles? Despite what Hollywood would have you believe, a car provides very little protection against bullets. Or if you really think some metal (or WH alternative) is better than none, just add a few (for example 1-4) points.

That way, civilian vehicles are indeed what civilian vehicles are meant to be; cheap transportation for civilians under civilized conditions. And if insurgents or desperate soldiers use civilian vehicles, adding armour plates would be the way to go....

Note that rugged vehicles for hazardous environments (thinking dangerous wildlife here) would likely have some armour.

And if colonists live in areas with dangerous xenos presence, they likely have cast off military vehicles or such.

Why not delete all armour for civilian vehicles? Despite what Hollywood would have you believe, a car provides very little protection against bullets. Or if you really think some metal (or WH alternative) is better than none, just add a few (for example 1-4) points.

Well if it has to go through the engine block...

Also this would make cars vulnerable to knives and claws and teeth. Not big claws and teeth, mind you. Dogs.