If you are providing custom training materials for clients, I've found it's much easier to just take photos of the trucks on site. I've contacted manufacturers in the past for use of images and it's kind of hit-and-miss as to whether you can ever find the right person to talk to and if they are willing to give you permission. If you have access to the vehicles, just take the photos yourself, it saves a lot of time.
If you absolutely want to use images from a manufacturer, I prefer to try to contact them via email (it saves time rather than holding on the phone, and their response provides a written record of the permission approval if granted). Send them an email with a clear and detailed description of which images you intend to use and exactly how you intend to use them.
Hi Joe
Have been in the same position. My usual approach is that where I can produce similar graphics reasonably easily I do so. That avoids copyright concerns.
If that is not possible I contact the company (usually by phone) to ask if it's possible to use their images - this usually results in a request to know the details of the use (which is fair enough). And provided the company is happy about the situation of use agreement is often given.
Alternately I might take my own images (still or video) at the worksite.
Or I ask the company requesting the training materilas to supply materials for me to use. As these are generally "owned" by the company (manuals or information supplied with the purchased forklift) and as you are producing materials for that company, then there are no issues.
If I want to use the materials in a way that there is a chance a supplier might react to my using the images, I digitally remove identifying marks (make, model, registration numbers etc) as a minimum, and may further change the image so that it is not obviously a certain make. Foe example with part of my training package i talk about forklift ratings by asking what the rating is of a forklift with the numbers 25 on the side (usually would mean a nominal rating of 2500 kg) and then go on to show what the actual ratings of that unit could be. Because the manufacturer might object to my message that the rating (in Australia) is never 2500 kg I used a very common forklift as my actual example but digitally altered the image to make it generic.
Trust this helps
John Lambert