>these last few months I've been working on building a navigation app called StreetWise+

Also there's one review that parrots what you wrote here, and another review that says the app "helped me during my college years navigating the streets of Compton".

It's not four years old lol, it's meant for people who are ages 4 or above is what that means. That one review probably meant it has helped him up to this point. It has only been on the app store for about a month. Sorry for any confusion!

Ah, makes sense. Is there any advanced methodology going on based on what you know of crime in Baltimore?

It uses machine learning to calculate local crime hotspots for recent crime based on police reports from a database and then assigns a danger score to each route based on the proximity of the route to nearby hotspots. The safest route with the lowest danger score is the default route the app highlights.

What database, just curious. Also how do you weight the crimes?

Most crime in Baltimore goes unreported, I think we all learned that from the federal consent decree. I don’t think this would be helpful or accurate if it’s based on police-confirmed crime reports.

You're right, there is definitely a lot of crime that goes unreported, however unreported crimes cannot be accessed from any sort of database so making such an app using unreported crimes would basically be impossible. Also while a lot of crime is unreported, that does not mean that using reported crimes would be entirely inaccurate as there is a lot of recent crime that does get reported in the database as I have done extensive testing with the app. Thanks for your feedback!

Crime is reported more in certain neighborhoods, and unreported or underreported more in other neighborhoods. Using the information from police-confirmed crime database would increase the disparity. Read up on the Black Butterfly. It’s disingenuous, if not dangerous, to provide something based on flawed information.

I would only see this being an issue if the user is traveling between multiple neighborhoods that cross into those underreported areas. The safest route is calculated by compared the relative safety of each route to each other based on proximity to local crimes, so if the app is used in neighborhoods with a decent reporting rate I don't think it would be disingenuous at all. The safest route is not being calculated by comparing different neighborhoods to each other, rather the routes that are all within one neighborhood.

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Baltimore is a city of neighborhoods, the safety of each environment varies block by block as well as neighborhood by neighborhood. Read any post asking for safety information for a specific neighborhood you will see responses indicating a certain neighborhood is safe “above XYZ street” or “until you get three blocks from ABC Blvd”. Downvote all you want, it’s poorly designed and doesn’t take the reality of the city into consideration.

As I stated in my last reply, the safest route is being calculated by comparing each route to each other, not by examining specific neighborhoods. As long as the route does not exclusively fall in a neighborhood where no crimes are being reported, a reasonable safety score can be calculated. I agree that there are some crimes that are not being reported, but no app can reliably get such data since it is unreported. I'm also working on adding a feature where users can manually report local crimes and then factor that into the safety algorithm. It's your choice if you want to download the app though, but there are definitely many people who could benefit from it.

Don’t think he’s going to just give you his business model in a Reddit post. LOL

Wasn’t there a fair amount of controversy when Microsoft introduced a similar concept a decade or so ago?

Edit: link - https://www.smartcitiesdive.com/ex/sustainablecitiescollective/why-microsofts-avoid-ghetto-app-takes-us-wrong-way/33775/

I would suggest using 2020 Census data for household income, in Baltimore at least that is a pretty good proxy for incidence of violent crime. There are certain places that should be avoided completely at night and census data paints a pretty clear picture.

I think user supplied crime data would have the potential to be even more disingenuous, given the likelihood that different demographics would respond to and comment about crime differently. Simply food for thought.

Well I need something if I'm going to consider the app. There are some specific things he should be saying about how it weights crimes, based on what we know of crimes committed in Baltimore. He hasn't said those yet. Another user is already pointing out additional flaws of the app.

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I love when google maps is like “drive through this gated/fenced property illegally” or “literally use this person’s long driveway as a road”

Noonlight is good, if you vaguely trust the police in your area

People need to use common sense. Baltimore (nor any big city) has been super safe during the wee hours of night. We have to stop thinking that we should be able to walk around as one does in rural areas. Stuff happens, try to use common sense.

As someone from a very very rural area, honestly I would feel safer in the “worst” parts of Baltimore than I would walking those rural backroads in some situations. Lots of shit can happen and there isn’t a single person for miles to hear a thing.

Great idea yet dystopian af

Not since I got my carry permit.

Yeah... Then it can just look at racial data, and stop beating around the bush. 🙄

But surely by sheer virtue of population density the statistical likelihood of being the victim of a crime is higher in the city no matter the eerie feelings one gets in rural areas. As for no one hearing you, there are plenty of city neighborhoods in the US that cries for help will not get a response - deaf ears are functionally the same as no ears, right?

“Turn into the incoming traffic on this one way street”

Using such flawed data and yet professing to have “the safest route possible” is disingenuous and potentially dangerous.

Unless you have data to back up your claims, no user should believe that the route they are being shown is actually the safest - potentially lulling users into a false sense of safety or inflated danger.

On top of this, the app tries to pass along something like “Safety” as if it is an objective measurement that we all agree on - but in reality, your subjective opinion (the scoring of your models) is making all of these choices for us.

Therefore you’ve really just made an app that is optimally useful for only the creator - and even then, it’s theres no indication that the route is indeed to safest.

One change you could make is by showing the under-hood of the model. For each route, show the safety score alongside the probability (and confidence intervals) of experiencing violent crime along each route (with huge asterisks) based on time traveled, size of walking party, gender, height-weight, and time of travel.

I’m willing to bet that the difference in score/probability/confidence level between the “best route” and the “more dangerous routes” are absolutely minimal - potentially making many serious distinctions you’re making from safe/unsafe useless.

I like the overall purpose of the idea, you would just need so much more data that does not yet exists for me to believe this app will work as intended at all.

Perhaps if we started collecting daily walking data for a few thousand baltimoreans across the city for like a few years, and then tracked their walking routes with the crimes they experienced, then maybe this app might work as intended.

Found the user with "Baltimore Stockholm Syndrome."

Walking at night face down in your phone instead of paying attention to your surroundings seems like the opposite of staying safe to me.

That's hyperbole a bit. But you're on the right track. I grew up in the boonies at the MD/PA line and can certainly say I've seen some shit.

Ive been to bars in So PA where I'd I'd just be buried in the woods if I crossed someone there. Almost run off the road by lifted trucks, meth heads following me out of a Walmart etc. Hell I've had someone run out with a shotgun when I turned around in their driveway.

However, those instances were far and few between the consistency and density of crime in the city. I live in an extremely quiet and safe neighborhood, but I can still hear the shots off of N Pkway a few times a week. Not even a month after I moved here, and there was a mass shooting within a mile of us

Now Ive been around the city for work and shows, so I don't feel unsafe but I can acknowledge that it's far easier to get in major trouble here.

Tldr: I learned street smarts in the boonies. But I apply them far more often in the city

Underrated comment

I had a thought like this when I was leaving DC and looking for a gas station and picked one that absolutely was not a smart decision at 10 at night and wished there was some layer of safer places to stop

Another big problem with this kind of data mining is that it doesn’t account for the base rate of route use.

Say there’s a very popular, busy pedestrian route that thousands of people walk every day. Over 6 months, there’s four crimes in the database for that stretch, but that’s out of hundreds of thousands successfully completed safe trips. Another route is much quieter—through neighborhood streets instead of up the main drag. It only has one crime in the database for the same period, but that’s out of only a few thousand successfully completed safe trips. If the app is just telling you that 1 < 4, it will recommend the quieter route, but that’s not necessarily the safer one. What you’d really want to know is the ratio of trips interrupted by crime : trips attempted. Otherwise the app is just reacting to where the people are and sending you away from them—and it’s common sense that an empty street is often more dangerous than a populated one.

That’s on top of the substantial problems with the database data that others have pointed to.

Brilliant points all around.

As you pointed out, this app completely hides the fact that the vast overwhelming majority of walking trips happen without any incident. Therefore, any incidents reported appear more like noise in the full-context of the data, rendering the predictive power of the model useless, and consequently rendering this app obsolete at the start.

You can call it whatever you want, but the reality is clear. Parts of Baltimore should be avoided unless you have a desire to experience the wonderful experience that is getting robbed or assaulted. Leaders who refuse to acknowledge these basic "street smarts" facts that everyone living here learns are why we end up getting idiots like Trump and the rest of the far right who just spew garbage, but at the same time get votes.

I thought about this while building the app. After the app calculates the safest route the gps navigation takes over (just like google maps), and the user is free to look at his surroundings instead of constantly having to look at his phone. Maybe you should download the app and try it yourself if you have any more questions.

i've never felt unsafe walking at night here. just be smart and stay aware of your surroundings 🤷🏾‍♀️

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I never understood the whole "racist argument" actually. If your safety is in peril, why would you consider socio-ethical ramifications of your choices? I've seen some mentally unstable people brandishing objects that could be used as weapons on the street. Would I take into consideration that they are possibly unfortunate victims of an unjust society (which I agree with) and walk by within the distance of their reach? For someone of a small stature like myself, I'd probably put the concern of safety over anything like that, to be honest.

I am literally using a database of real-time verified crime data that gets updated hourly with new, very recent crime reports that gets factored into the algorithm to determine the safest route. How is that not "backed up by data"? You are also right that a lot of the time the safety score for each route are very similar, which is why the user has the option to choose between different routes (they are not just being forced to take one route) and pick one that optimizes their preferences for both safety and speed.

He's just using the crime data BPD publishes. The dataset is subject to both non-response bias (ppl don't report all crime to the police) and fluctuations due to the changes in police deployments or dealers moving between corners, meaning even if it could get good predictions it's a lagging indicator.

Also, this all assumed that BPD is reporting their arrests on time. That dataset gets updated sporadically, it's not reliable for this kind of real time use.

Never mind the problem of having your phone out to look at directions in an unsafe area.

OP I applaud you for putting together a portfolio project, but please consider taking it off the app store before this gets someone killed.

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Imo historically avoidance is often a popular step for at large and wealthy aspects of society, that app would kinda make it easier to avoid the conversations behind certain things because it would kinda cut out a whole section of a city that maybe needs more interaction. Gentrification in small cities like Baltimore already showcase the glaring double side of the populations, giving richer or well off people the chance to not even see things that they might have a hand in creating or changing won't help. It's 2 sided, the individual will want safety but the society should make it sage, companies like Microsoft can literally do both so to take a side seems like it could have deeper consequences.

Many studies have shown that past crimes are indicative of future crimes happening at similar locations in the future, which is what inspired me to build the app. Hence the model definitely has some predictive value and is not obsolete at all, imo.

What do you make of the argument that the app won’t have a realistic measure of safety for Black users who may be more likely to be subjected to police harassment in some statistically low-crime neighborhoods (because harassment and assault by police aren’t recorded as crimes)?

My understanding is that generally speaking you’re more likely to be the victim of a crime in cities, but you’re usually more likely overall to be killed by external factors in rural areas. This is because rural areas have far more fatal car accidents, drownings, animal attacks, etc. So if the goal is just avoiding death you’re usually safer in cities (though not sure if this holds true for cities with higher than average homicide rates like Baltimore).

This is a fair point, black users could be more subject to police brutality, but like you said, that doesn't fall into the category of crimes. The safety the app calculates is solely related to crimes, and I state in my disclaimer that every user is still responsible for his or her safety/life at the end of the day. The user also has the option to choose between a plethora of route options that optimize his preferences for both safety and speed, they are not being forced to take just one route.

I only have my experiences and those of people choose to me, but I don't see this working because:

1. I think people who use GPS rely on the visual side moreso than the audio side.
2. I think people who walk home safely at night in urban areas tend to be more street smart. Those people already have a familiar route. Taking a new route in the dark seems like a recipe for disaster. People flub GPS directions all the time.
3. I think the people who are uncomfortable walking are going to call an Uber.
4. I think people who are uncomfortable both walking and using Uber at night aren't the type of people to be going out at night anyway.
5. I think people already uncomfortable going out in the dark at night aren't going to be suddenly more comfortable.
6. If it were to take off on a large scale, criminals would just use the app to see what routes people walk. I would just put in a popular bar address and a college campus address and I know what route is "safest".

I think your heart is in the right place but I just don't see it working out. Good luck to you, but I'd take your app development skills and try a different app.

All is my opinion, though

Okay, but HOW MUCH predictive power?

“Some predictive value” is no different from “almost no predictive value at all”

Can this app accurately predict whether or not someone will have an incident on any given path? Of course not, bc if the data was that granular the police would just intervene and prevent the crime from happening in the first place - and of course, this is ridiculous.

The amount of data you would need to prove that simply does not exist.

And if you think simply saying “many studies” is convincing, then you are sorely mistaken. Aren’t you trying to promote this app? Are you really seeking to make people safer or is this just a cash grab, profiting off of some people’s innate fears?

1. People using GPS definitely use the visual side as a guide, but to say they are glued to their phones is definitely an exaggeration.

2. This is true, there are definitely some people who know the streets very well and don't need the know the safest route. However, to say most people who walk home at night fall in this category is also an exaggeration.

3. But what if the person doesn't want to waste money on an Uber?

4. I think this app could have a lot of use for college students walking to parties late at night or little kids who are walking home from school.

5. I think the app will definitely help those walking at night feel safer knowing the locations of nearby crimes.

6. I also thought about this while building the app. The user has the ability to choose between a plethora of options that maximize their preferences for safety and speed, they are not just being forced to choose one route. Moreover, the routes are all calculated from where the user is located, so different users will get different routes depending on their individual locations in the city. Lastly, the database is getting updated hourly with new data from the past day that could change the recommended routes, so if a criminal catches someone it would most likely be due to random chance rather than because the app is making the user more vulnerable.

It’s just not true that the absolute number of crimes “should” correlate with the ratio of trips interrupted by crime : trips attempted, even if both routes have been taken at least some minimum number of times (which your model doesn’t have any way of knowing, anyway). If you don’t understand this very basic bit of data science, it’s totally reckless for you to be offering people advice on where to walk.

Look, there were 485 murders in NYC in 2021, compared to 337 in Baltimore in the same period. But we all know better than to say that Baltimore is safer than NYC, because NYC has many times more people in it than we do. You have to correct for the base rate of population by comparing murders/100k residents or something. When you do that, you see that the count doesn’t correlate with the relative risk ratio at all!

If you don’t have the information you need for the denominator of the relative risk ratio, there’s no amount of “testing” that can show your model works.

I did extensive market research before pursuing this idea, and seeing all the studies on the correlation is what inspired me to build it. In fact similar apps also use a similar principle to calculate areas where future crimes are likely to occur. An example of such an app is WalkSafe+. It's your choice if you want to believe that.

You're right the app cannot predict whether someone will have an incident, but it definitely lowers the chance a considerable amount. Hence "some predictive value" is most certainly different from "no predictive at all." It's your choice if you want to download the app though and don't think it's benefitting you. I don't think you speak for everyone though.

This is a good point, but as I stated previously, current crime hotspots do indeed have predictive value of where future crimes will occur. Moreover, I am not forcing the user to take a specific route, they have a plethora of options to choose based on their preferences for both speed and safety. If you don't believe me you don't have to download the app.

Also your whole comparison of Baltimore to NYC is completely dumbfounded because the user will be choosing between routes that go through the same city, with all route options having being taken a similar number of times. Hence if one route has a significantly greater number of crime hotspots that will almost certainly correlate with the crime:trips attempted ratio. Also as I said previously, the user can choose between multiple options and I am not forcing him to take any specific route.

Edit: brightbehaviorist I totally understand what you're saying that the crime:trips ratio would be a better indicator of the safety than just crimes, and I am working on integrating this into the algo. However, I think it is still very useful to see local crime hotspots along the route you're taking, and I has said before, the user can choose between a plethora of options based on their preferences (like google maps). Thanks for your feedback!

1. The user has the option to choose between a plethora of options based on his preferences for both speed and safety, they are not just confined to take one specific route.

2. With or without the app people will always be killed. I also state in my disclaimer that the app only gives you the lowest chance of a crime happening and does not guarantee that one will not happen. The safety is still the responsibility of the user.

3. I have done extensive testing with the database and it actually returns very recent crimes (within the last day) up till the last week. It is also constantly updated hourly with new crimes that can change the recommended route based on the algorithm.

Hence, I disagree with all of your points.

Please show me where BPD is posting “real-time verified crime data that gets updated hourly.”

Not using BPD

So then where is this data coming from? Lots of us here have trouble trusting BPD reporting in the first place, but if it’s not their data then whose? Pretty sure the only source of crime data for the city would be from police

From an api that performs web scraping on several datasets across the US. Based on the testing I have done the crimes are extremely recent, from within the last day to the past week, and new ones are inputted each day that can change the recommended route. I don't feel comfortable sharing the exact source as that might give too much info away for competitors.

Also if you don't trust the reporting/data source you can still use the app to see the locations of nearby crimes, and the user is not restricted to take one route, he has a plethora of options to optimize his preferences for both safety and speed.

If these are public datasets you should have no problem sharing them and letting potential customers see where exactly you’re pulling data from. Otherwise, they have no reason to trust it. I see you’ve posted in multiple other cities trying to shill this same service. Hopefully, the fact that this post has gotten the most traction in two weeks, and the fact that most here are refuting your claims or want to see the data shows you that your idea, while well intentioned, is not feasible. At least not the way you’re presenting it.

If I share the exact dataset that will literally be a recipe for someone to build a similar app, especially if I do that in a reddit post. If you want, you can email me at streetwisesafe@gmail.com and we can chat over email there and I can be more specific. Also every claim that has presented I have refuted, so the app is definitely both well-intentioned and feasible.

You are the only person who has asked to see the actual data source and cannot trust it without knowing that, not "most here."

I disagree whole heartedly and have no interest in keeping this conversation with a brick wall going over email. Your app’s download numbers will reflect the flaws in your concept.

Any logical reason why you "disagree whole heartedly?" Also if you download the app and click the info icon it explains how the data is being collected. I just don't want to share that on a reddit post is all.

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you made good points. plus, there are other ways to keep yourself safe at night here without any apps.

Very unconvincing.

-What is the predictive power? Precision and Specificity, confidence intervals?

“definitely lowers the chance a considerable amount”

Explain. How did you come to this conclusion? What are you even considering is “a considerable amount”?

Can you even currently calculate the correlation between your “danger score” and predicted crime?

You’re selling this app as safety, a mistake many apps and service solutions offer. But this app does not actual make people safer. You haven’t demonstrated this and it doesn’t look like you intend to. It looks like you don’t care if this app actual makes people safer - just worried about the “market” and the download rate. Which is sorta okay…..(because anyone relying purely on an app to be safe is insane in the first place)

You’re right, this app isnt for me, and idk who it’s for. I wish you luck in hopes that this improves and that you really rethink your strategy. Nevertheless, making an app is a big task - so congrats on getting this far.