Neighbour's dog allowed to scare 3 year old son with autism

Have you asked Citizens Advice Bureau about this? Also have you approached a local councillor. The situation with noisy dogs is down to local bye-laws and how effectively they are implemented. It certainly isn't easy to resolve because the onus is on the person making the complaint to prove nuisance.

Children particularly should feel safe in a public place. Though autism might make a child more acutely sensitive that shouldn't constrain finding a resolution to a noisy dog. The fact that it is noisy in public also suggests the owner has not taken sufficient care in training: dogs being pack animals look for a leader to keep it in check. It sounds like this lady hasn't taken her responsibilities seriously.

In my experience local authority officials do tend to smokescreen the situation in the hope you wont inconvenience them with the paperwork, and will go away a try to find another solution. You need to press your case for action with a senior official if possible with the help of a councillor. Some would say I'm being too pushy and over the top, but often you do have to take this level of action to get what you are entitled to.

All the same, even if you can get some action, the legal constraints on what to do often amount to no more than someone going round to ask the lady to show more consideration.

There is a debate that arises about the legality of reprisals: for example dog whistles and compressed air klaxons may have legal constraints on you having or using one, but it can also "train" the dog not to bark.  Also throwing some food into the street for the dog to eat (diversion tactics) may incur a fine for littering, but on balance might create a situation where the dog gets a reward for barking in the street, you keep rewarding it - but at least your son gets some peace while the dog eats. You can put stuff on your perimeter fence that gets the dog more interested in smells, but that could attract other dogs. There's a fine line in law, but to a certain extent you could look at just "muddying the water" a little bit, so it isn't just her dog getting at your child.

Also keep detailed records and if possible record audio or even video, as long as within the law.

There is a distinction between private and local authority property. If it is council property there are rules on keeping pets and keeping them in order. 

Have you asked Citizens Advice Bureau about this? Also have you approached a local councillor. The situation with noisy dogs is down to local bye-laws and how effectively they are implemented. It certainly isn't easy to resolve because the onus is on the person making the complaint to prove nuisance.

Children particularly should feel safe in a public place. Though autism might make a child more acutely sensitive that shouldn't constrain finding a resolution to a noisy dog. The fact that it is noisy in public also suggests the owner has not taken sufficient care in training: dogs being pack animals look for a leader to keep it in check. It sounds like this lady hasn't taken her responsibilities seriously.

In my experience local authority officials do tend to smokescreen the situation in the hope you wont inconvenience them with the paperwork, and will go away a try to find another solution. You need to press your case for action with a senior official if possible with the help of a councillor. Some would say I'm being too pushy and over the top, but often you do have to take this level of action to get what you are entitled to.

All the same, even if you can get some action, the legal constraints on what to do often amount to no more than someone going round to ask the lady to show more consideration.

There is a debate that arises about the legality of reprisals: for example dog whistles and compressed air klaxons may have legal constraints on you having or using one, but it can also "train" the dog not to bark.  Also throwing some food into the street for the dog to eat (diversion tactics) may incur a fine for littering, but on balance might create a situation where the dog gets a reward for barking in the street, you keep rewarding it - but at least your son gets some peace while the dog eats. You can put stuff on your perimeter fence that gets the dog more interested in smells, but that could attract other dogs. There's a fine line in law, but to a certain extent you could look at just "muddying the water" a little bit, so it isn't just her dog getting at your child.

Also keep detailed records and if possible record audio or even video, as long as within the law.

There is a distinction between private and local authority property. If it is council property there are rules on keeping pets and keeping them in order.