Hooking up a certain trailer to a certain vehicle is the specific responsibility of the driver, excepting cases of a light trailer where this choice is not made by the driver but already appears on the vehicle logbook. 
Let us therefore analyse only the cases in which the driver must understand by himself if he can or cannot tow a certain trailer by evaluating weights and sizes. 
Weights
  We take it for granted that the reader has a vehicle with a tow-bar, already approved and noted on the logbook. The logbook will therefore show maximum width and weight of the towed trailer. 
Anyone can easily see that   for automobiles, multi-purpose vehicles and campers the value of the maximum towable weight   never exceeds the automobile tare. This limit which, we repeat, appears on the vehicle logbook at the moment of tow-bar inspection and approval, almost always reassures us that the so-named “towing ratio” is respected. In fact for our trailers, which have mechanical inertia braking, the maximum towing ration would be 0.8 (rounded up to 100 kilos) but if the towable weight in the logbook does not exceed the vehicle tare then 0.8 will almost always be respected. 

There could be some problems with a non-braking trailer, i.e. without any braking device. In this case the maximum   towing ratio admissible is 0.5 and therefore you need to be more careful because the towable weight in the vehicle logbook is usually 50% greater than the vehicle tare and it may happen that the non-braking trailer, no matter how small, cannot be towed by our vehicle, or may be towed only when our vehicle is fully laden. 

Let’s take an example. An economy car has a tare of 700 kilos and the overall weight fully laden is 1.000 kilos. With the tow-bar mounted and approved, the maximum towable weight will be shown on the logbook, let us suppose 600 kilos, i.e. a value lower than or equal to the tare. At this point let us suppose that we want to tow a trailer with a tare of 350 kilos and an overall fully laden weight of 600 kilos and which at that moment weighs 500 kilos. Let us examine the towing possibilities when our vehicle is unladen (i.e. it weighs the same as the tare of 700 kilos). If the trailer has inertia brakes the match-up is correct because the trailer weight (500 kilos) is less than the towable weight (600 kilos) and at the same time comes within the towing ratio (80% of 700 kilos is 560 kilos to be rounded up to 600 kilos). If on the other hand the trailer has no brakes the match-up is not possible because 50% of 700 kilos is 350 kilos. If, lastly, the trailer is empty, i.e. weighs 350 kilos, then the match-up is possible. However, the case demonstrated is really hypothetical because existing non-braking trailers are very light (overall fully laden weight around 300 kilos). 

Let us summarise the basic concept: towability is a driving condition entrusted to the driver’s responsibility and he must, each time, judge towing possibilities while observing the limitations of:
  • Towing weight shown in the vehicle logbook
  • Maximum towing ratio (0,8 for trailers with inertia braking, 0,5 for non-braking trailers);

and in accordance with special driving conditions given by:

  • Overall vehicle weight;
  • Overall trailer weight.

We remind you that the overall weight of any vehicle in any running condition must necessarily come within the tare and the overall fully laden weight. 
As a practical rule, since it cannot be presumed that everyone will weigh vehicle and trailer before each trip, it is advisable to remain within the safety margins roughly given by comparison between the towable weight shown in the vehicle logbook and the overall fully laden weight shown in the trailer logbook. We should doubt this rule when:

  • The trailer is fully laden and the vehicle absolutely unladen;
  • The trailer has no brakes, is fully laden, and the vehicle, over and above being unladen is a small economy vehicle.

Width and projections
The maximum tow width, like the weight, is also added to the vehicle logbook at the moment of the tow-bar approval inspection test.
For a light trailer there is nothing else to add. For caravans and T.A.T.S (Transport of Tourism and Sports Equipment). however we must remember an extra condition: the width of these trailers must never exceed the sum of the overall width of the vehicle plus 70 cm. (rounded up to the next 5 cm.). So take care when you hook up a caravan or a T.A.T.S.: the width of the trailer must respect the strictest limit between the two (the vehicle logbook towable width or the vehicle width plus 0.7 metres).

Still on the subject of towing caravans and T.A.T.S. there is the obligation of a right as well as a left rear-view mirror. The external mirrors, also the detachable type, must not project more than 20 cm. from the vehicle's overall outline (towing vehicle or trailer, whichever is wider).

Again with regard to respecting the maximum towable width, we add that for T.A.T.S., whose outline is defined by the equipment transported rather than the vehicle itself, the boat may project 30 cm. per side in relation to the external edges of the rear sidelights. Equipment difficult to see such as masts, bars, plates etc, must remain within the outline of the trailer it self. 

Rear projection beyond the limit shown on the logbook (the famous 3/10 of the length of the trailer, only for transporting indivisible things and with suitable white-red panels) should not however lighten the weight on the trailer hook, meaning that it is better not to break the law on projecting loads in order to avoid jeopardising the safety of the tow.
Driving licence required for towing
First of all let us get rid of a recurring doubt: when the towing vehicle has an overall fully laden weight which is less than or equal to 3.500 kg (shown on the logbook) then the driver must have licence B or BE, but not C or CE as some believe. This means that since all automobiles and multi-purpose vehicles and almost all campers come within 3.5 T. of overall fully laden weight, to town our boat trailer all you need is licence B or BE. Only when the towing vehicle exceeds 3.5 T overall fully laden weight (campers or trucks) is licence C or CE necessary. But let's take things in order.
Category B towing vehicle
(automobiles, campers and trucks up to 3.5 T overall fully laden weight).
  • Light trailer (overall fully laden weight up to 750 kg). Licence B is still sufficient for this combination. To tow a light trailer licence B is therefore sufficient and this is perfectly coherent with the definition of the light trailer as an integral part of the towing vehicle.
  • Non-light trailer (overall fully laden weight greater than 750 kg, whose overall fully laden weight does not exceed the unladen weight of the towing vehicle).
     Licence B is still sufficient only if the sum of the overall fully laden weight (as per the logbook) of the towing vehicle and trailer is less than or equal to 3.5 T; otherwise, i.e. if the sum exceeds 3.5 T, license BE is required
  • Non-light trailer (overall fully laden weight greater than 750 kg, whose overall fully laden weight exceeds the unladen weight of the towing vehicle).
    Licence BE is required.

Some considerations on the subject. Firstly, the category of licence necessary derives from the combination of data shown in the logbook as opposed to the prima facie towable characteristics entrusted to the responsibility of the driver.

Secondly, there may be cases in which the overall fully laden weight of the vehicle and trailer exceeds 3.5 T but licence B is still sufficient: here we are dealing with the hook-up of a light trailer to a vehicle which is already close to 3.5 T.

Lastly, more in-depth information on T.A.T.S.. Some have an overall fully laden maximum weight (in the logbook) and a minimum (in the use and maintenance manual): the logbook takes precedence for deciding on the type of licence required.
Category C towing vehicles
(campers and truck-trailers over 3.5 T overall fully laden weight )
  • Light trailer (overall fully laden weight up to 750 Kg). Licence C required. The light trailer therefore never requires category E.
  • Non-light trailer (overall fully laden weight over 750 Kg) Licence CE required.

It's not out of place to refresh our memories on the licence hierarchy.
If it's true that licence D is superior to C and B, it's equally true that the extension E follows in a parallel way the categories B, C and D but is not linked with them. Licence C, for example, is superior to B but not to BE, so someone who already has BE and then takes C will have a C+ BE licence and not a CE. The CE is superior to the BE. In order to take the BE and CE licences, as well as having to have, respectively, category B or C, you must take an oral exam in theory, the programme of which is the same for all the E licences, and a practical driving exam which is different for the BE and the CE (the type of vehicle with which you take the test is different).
Special obligations and standards of behaviour
When you tow a light trailer it is as if your were driving a single vehicle inasmuch as the trailer is considered an integral part of the towing vehicle. The standards to observe are therefore the same as for an ordinary automobile; the speed limits for all are: 50 kph in built-up areas, 70 kph on urban freeways (marked by special road signs), 90 kph on non-urban secondary roads, 110 kph on main non-urban roads (super-highways) and 130 kph on motorways. So when the trailer is a registered tow, even though licence B is sufficient we are driving a vehicle with trailer and must drive with all the prescribed due care and attention.

First of all, the speed limits. Away from built-up areas it is 70 kph and, on the motorway, 80 kph. Moreover we are obliged to stick two reflecting signs to the rear of the trailer showing these limits. No exceptions are envisaged for T.A.T.S. so we should try to put these signs in such a way that they are stable but can be removed when we haul the boat or dinghy. Keep in mind that the fines for speeding, already high, are doubled in the case of a vehicle with trailer.

Secondly, be careful about parking. When detached from the towing vehicle, trailers must not be parked in built-up areas.


Lastly, with regard to periodic inspection testing of trailers and vehicles, you are advised to check each January with the Provincial Office of Civil Motorization because there is a constant evolution in bringing the Italian deadlines into line with European ones.
Glossary
TARE: unladen vehicle weight; the tare is shown in the logbook.

UNLADEN WEIGHT: weight of unladen vehicle without driver; it is equal to the tare less 70 kilos for the driver.

OVERALL WEIGHT: weight of the vehicle ready for the road; it is a running condition and therefore variable depending on the load; the overall weight must never exceed the weight of the maximum permissible laden weight.

CAPACITY: load on vehicle.

MAXIMUM LOAD: the capacity shown in the logbook; the difference between the overall laden weight and the tare.

OVERALL LADEN WEIGHT: maximum weight of laden vehicle; the overall laden weight is shown in the logbook.

TOWING RATIO: ratio of the overall weight of the trailer and that of the vehicle.
Penalties
  • Driving without the necessary category of licence (for example licence B instead of BE):
    fine: ITL 200.000;
    accessory penalty: loss of licence for 1 to 6 months
  • Tow-bar and/or light trailer not noted in vehicle logbook:
    fine: ITL 500.000;
    accessory penalty: confiscation of logbook.
  • Trailer (excluding light trailers) not registered:
    fine:ITL 1.000.000
    accessory penalty: confiscation of vehicle.
  • Match-up that does not respect the towing criteria:
    fine: ITL 100.000;
  • Breaking speed limit for vehicle with trailer: fine:
    a) limit exceeded by less than 10 kph: ITL 100.000;
    b) limit exceeded by more than 10 kph: ITL 400.000;
    c) limit exceeded by more than 40 kph: ITL 1.000.000;
    accessory penalty: loss of licence for 1 to 6 months (2 to 8 months for a subsequent offence).
  • Failure to put speed limit signs on rear of trailer:
    fine: ITL 30.000.
  • Detached trailer parked in built-up area:
    fine: ITL 50.000 (for each day's parking).
  • Driving without periodic test certificate:
    fine: ITL 200.000;
    accessory penalty: confiscation of logbook (on motorway vehicle also withdrawn from circulation).