Installation of bollards is more likely to be about a trip hazard, than visual.
It is also possible if the committee hasn’t turned its mind to bollards, they say “no” until they have had time to consider.
I would suggest that you do the research for them and submit permission for a product that is recessed into the floor, could be telescopic and when upright is the sufficient height that a car can see it when reversing. There may need to be consultation with a structural engineer to determine the depth of recess without compromising the structural integrity (if it is not a slab on the ground). It may also need to be lit, if there is insufficient ambient lighting.
The product needs to address the risk for the owners corporation whilst balancing the needs of owners. If you propose a surface mounted solution, then add that you will provide signage and continuously have “public liability” for your private property and that you will indemnify the owners corporation for any injury caused from your installation and provide a certificate of currency every 12 months.
Do the research, provide alternatives and submit to the committee for consideration. The committee needs to act reasonably. This doesn’t mean they have to say Yes to your proposal, but it does mean they need to weigh the pro’s and con’s and give reasons as to why you can or can’t have the bollard.
If you still feel aggrieved, then you can then contest the committees decision at VCAT.